98 results on '"Xinchuan Huang"'
Search Results
2. PPD: A Scalable and Efficient Parallel Primal-Dual Coordinate Descent Algorithm
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Qiong Luo, Xinchuan Huang, Zhongheng Yang, and Hejun Wu
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Scheme (programming language) ,Computer science ,Degree of parallelism ,Function (mathematics) ,Computer Science Applications ,Dual (category theory) ,Acceleration ,Computational Theory and Mathematics ,Scalability ,Parallelism (grammar) ,Coordinate descent ,Algorithm ,computer ,Information Systems ,computer.programming_language - Abstract
Dual Coordinate Descent (DCD) is one of the most popular optimization methods. The parallelization of DCD is difficult, as DCD is sequential in nature. As such, simultaneously running multiple DCD threads on batches of data elements causes result inaccuracy and slow convergence, due to the concurrent updates of multiple coordinates. Some parallelization methods adopt separable approximate functions that depend on the degree of parallelism. Such dependencies result in both poor scalability and slow convergence. To address these challenges, in this paper we present a new parallel primal-dual algorithm for DCD, called PPD. In PPD, the block data distribution is utilized to obtain a new approximate function that is independent from the parallelism. Subsequently we design a novel primal-dual acceleration scheme based on PPD to approach the optimal solution closely and quickly. We demonstrate the advantages of PPD in terms of scalability and efficiency through experiments.
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- 2022
3. Complete, Theoretical Rovibronic Spectral Characterization of the Carbon Monoxide, Water, and Formaldehyde Cations
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Ryan Fortenberry, Megan Davis, and XINCHUAN HUANG
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quantum chemistry ,coupled cluster theory ,Chemistry (miscellaneous) ,astrochemistry ,UV/Vis spectra ,Organic Chemistry ,Drug Discovery ,Molecular Medicine ,Pharmaceutical Science ,Physical and Theoretical Chemistry ,computational spectroscopy ,rovibronic spectra ,Analytical Chemistry - Abstract
New high-level ab initio quartic force field (QFF) methods are explored which provide spectroscopic data for the electronically excited states of the carbon monoxide, water, and formaldehyde cations, sentinel species for expanded, recent cometary spectral analysis. QFFs based on equation-of-motion ionization potential (EOM-IP) with a complete basis set extrapolation and core correlation corrections provide assignment for the fundamental vibrational frequencies of the A˜2B1 and B˜2A1 states of the formaldehyde cation; only three of these frequencies have experimental assignment available. Rotational constants corresponding to these vibrational excitations are also provided for the first time for all electronically excited states of both of these molecules. EOM-IP-CCSDT/CcC computations support tentative re-assignment of the ν1 and ν3 frequencies of the B˜2B2 state of the water cation to approximately 2409.3 cm−1 and 1785.7 cm−1, respectively, due to significant disagreement between experimental assignment and all levels of theory computed herein, as well as work by previous authors. The EOM-IP-CCSDT/CcC QFF achieves agreement to within 12 cm−1 for the fundamental vibrational frequencies of the electronic ground state of the water cation compared to experimental values and to the high-level theoretical benchmarks for variationally-accessible states. Less costly EOM-IP based approaches are also explored using approximate triples coupled cluster methods, as well as electronically excited state QFFs based on EOM-CC3 and the previous (T)+EOM approach. The novel data, including vibrationally corrected rotational constants for all states studied herein, provided by these computations should be useful in clarifying comet evolution or other remote sensing applications in addition to fundamental spectroscopy.
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- 2023
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4. The mid-infrared molecular inventory towards Orion IRc2
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Sarah Nickerson, Naseem Rangwala, Sean W. J. Colgan, Curtis DeWitt, Jose S. Monzon, Xinchuan Huang, Kinsuk Acharyya, Maria N. Drozdovskaya, Ryan C. Fortenberry, Eric Herbst, and Timothy J. Lee
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Space and Planetary Science ,530 Physics ,Astrophysics of Galaxies (astro-ph.GA) ,520 Astronomy ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
We present the first high spectral resolution mid-infrared survey in the Orion BN/KL region, covering 7.2 to 28.3 micron. With SOFIA/EXES we target the enigmatic source Orion IRc2. While this is in the most prolifically studied massive star-forming region, longer wavelengths and molecular emission lines dominated previous spectral surveys. The mid-infrared observations in this work access different components and molecular species in unprecedented detail. We unambiguously identify two new kinematic components, both chemically rich with multiple molecular absorption lines. The "blue clump" has vLSR = -7.1 \pm 0.7 km/s and the "red clump" 1.4 \pm 0.5 km/s. While the blue and red clumps have similar temperatures and line widths, molecular species in the blue clump have higher column densities. They are both likely linked to pure rotational H2 emission also covered by this survey. This work provides evidence for the scenario that the blue and red clumps are distinct components unrelated to the classic components in the Orion BN/KL region. Comparison to spectroscopic surveys towards other infrared targets in the region show that the blue clump is clearly extended. We analyze, compare, and present in depth findings on the physical conditions of C2H2, 13CCH2, CH4, CS, H2O, HCN, H13CN, HNC, NH3, and SO2 absorption lines and an H2 emission line associated with the blue and red clumps. We also provide limited analysis of H2O and SiO molecular emission lines towards Orion IRc2 and the atomic forbidden transitions [FeII], [SI], [SIII], and [NeII]., Accepted to ApJ; 44 pages, 14 figures, 13 tables
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- 2022
5. Ames-2021 CO
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Xinchuan, Huang, David W, Schwenke, Richard S, Freedman, and Timothy J, Lee
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A highly accurate CO
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- 2022
6. IMPROVED CO2 IR LINE LIST FOR 1500K - 3000K
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Xinchuan Huang, Timothy Lee, Richard Freedman, and David Schwenke
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- 2022
7. AMES-1 296K IR LINE LISTS FOR CS2 ISOTOPOLOGUES
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Xinchuan Huang, Timothy Lee, and David Schwenke
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- 2022
8. AMES-1 296K IR LINE LISTS FOR OCS ISOTOPOLOGUES
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Xinchuan Huang, Timothy Lee, and David Schwenke
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- 2022
9. RECENT UPDATES TO THE HITEMP DATABASE
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Robert Hargreaves, Laurence Rothman, Eamon Conway, Xinchuan Huang, and Iouli Gordon
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- 2022
10. What It Takes to Compute Highly Accurate Rovibrational Line Lists for Use in Astrochemistry
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Timothy J. Lee, David W. Schwenke, and Xinchuan Huang
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Line list ,Astrochemistry ,010405 organic chemistry ,Computer science ,General Medicine ,General Chemistry ,Rotational–vibrational spectroscopy ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Computational physics - Abstract
ConspectusWe review the Best Theory + Reliable High-Resolution Experiment (BTRHE) strategy for obtaining highly accurate molecular rovibrational line lists with InfraRed (IR) intensities. The need for highly accurate molecular rovibrational line lists is twofold: (a) assignment of the many rovibrational lines for common stable molecules especially those that exhibit a large amplitude motion, such as NH
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- 2021
11. AI-3000K Infrared line list for hot CO2
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Xinchuan Huang (黄新川), Richard S. Freedman, Sergey Tashkun, David W. Schwenke, and Timothy J. Lee
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Physical and Theoretical Chemistry ,Spectroscopy ,Atomic and Molecular Physics, and Optics - Published
- 2023
12. Highly Accurate Quartic Force Field and Rovibrational Spectroscopic Constants for the Azirinyl Cation (c-C2NH2+) and Its Isomers
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Partha P. Bera, Timothy J. Lee, and Xinchuan Huang
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Cyclopropenylidene ,010304 chemical physics ,Chemistry ,Electronic structure ,Rotational–vibrational spectroscopy ,Configuration interaction ,010402 general chemistry ,01 natural sciences ,Molecular physics ,0104 chemical sciences ,chemistry.chemical_compound ,0103 physical sciences ,Physics::Atomic and Molecular Clusters ,Molecule ,Isotopologue ,Perturbation theory (quantum mechanics) ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Basis set - Abstract
The azirinyl cation is an aromatic cyclic molecule that is isoelectronic with cyclopropenylidene, c-C3H2, and c-C3H3+. Cyclopropenylidene has been shown to be ubiquitous, existing in many different astrophysical environments. Given the similar chemistry between C and N, and the relative abundances between C and N in astrophysical environments, it is expected that there should be aromatic ringed molecules that incorporate N in the ring, but as yet, no such molecule has been identified. To address this issue, the present study uses high levels of electronic structure theory to compute a highly accurate quartic force field (QFF) for the azirinyl cation and its two lowest lying isomers, the cyanomethyl and isocyanomethyl cations. The theoretical approach uses the singles and doubles coupled-cluster method that includes a perturbative correction for connected triple excitations, CCSD(T), together with extrapolation to the one-particle basis set limit and corrections for scalar relativity and core-correlation. The QFF is then used in a second-order vibrational perturbation theory analysis (VPT2) to compute the fundamental vibrational frequencies and rovibrational spectroscopic constants for all three C2NH2+ isomers. The reliability of the VPT2 vibrational frequencies is tested by comparison to vibrational configuration interaction (VCI) calculations, and excellent agreement is found between the two approaches. Fundamental vibrational frequencies and rovibrational spectroscopic constants for all singly substituted 13C, 15N, and D isotopologues are also reported. It is expected that the highly accurate spectroscopic data reported herein will be useful in the identification of these cations in high-resolution experimental or astronomical observations.
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- 2019
13. 14NH3 ROVIBRATIONAL IR ANALYSIS AT 6000 CM−1
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Xinchuan Huang, Timothy J. Lee, Keeyoon Sung, David W. Schwenke, and Geoffrey C. Toon
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Analytical chemistry ,Rotational–vibrational spectroscopy - Published
- 2021
14. TOWARD 0.1% UNCERTAINTY FOR CO2 THEORETICAL IR INTENSTIES
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Timothy J. Lee, Xinchuan Huang, and David W. Schwenke
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- 2021
15. Isotopologue consistency of semi-empirically computed infrared line lists and further improvement for rare isotopologues: CO2 and SO2 case studies
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David W. Schwenke, Xinchuan Huang, and Timothy J. Lee
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Radiation ,010504 meteorology & atmospheric sciences ,Transition dipole moment ,Extrapolation ,Rotational–vibrational spectroscopy ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Computational physics ,Quartic function ,Outlier ,Isotopologue ,Rotational spectroscopy ,Spectroscopy ,Order of magnitude ,0105 earth and related environmental sciences ,Mathematics - Abstract
The semi-empirical molecular rovibrational IR line lists, such as ExoMol, TheoReTs, and Ames, combine the experimental accuracy and theoretical power to reach better than 0.1 cm−1 accuracy for line positions and better than 80–90% agreement for line intensities. The quality of these existing semi-empirical IR lists allows further improvements of intensity and line positions for those unobserved minor isotopologues. This paper presents our new BTRHE (Best Theory + Reliable High-resolution Experiment) strategy implementation. For line intensity, the isotopologue consistency and the patterns of mass dependence in the Ames-296 K SO2 and CO2 IR lists are quantitatively presented along the mass-inverse coordinates. The consistency and patterns are better than those in existing experimental data. The methodology proposed here can be used to identify inconsistencies, outliers, and mistakes in intensities, and help improve Effective Dipole Model (EDM) and molecular IR databases. We call for an experimental study on the 50006 and 60007 bands of CO2 628. For line position predictions, a simple approach combining the variational IR line lists with Effective Hamiltonian (EH) model may refine the effective rotational constants A0/B0/C0 and quartic centrifugal distortion constants of minor isotopologues. The prediction accuracy may be improved by two orders of magnitude, i.e. reaching 0–5 MHz prediction accuracy in the range of J
- Published
- 2019
16. Quantitative validation of Ames IR intensity and new line lists for 32/33/34S16O2, 32S18O2 and 16O32S18O
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David W. Schwenke, Xinchuan Huang, and Timothy J. Lee
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Physics ,Radiation ,010504 meteorology & atmospheric sciences ,Rotational–vibrational spectroscopy ,Quantum number ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Computational physics ,Dipole ,symbols.namesake ,Stark effect ,symbols ,Isotopologue ,HITRAN ,Hamiltonian (quantum mechanics) ,Ground state ,Spectroscopy ,0105 earth and related environmental sciences - Abstract
The quality of Ames-296K SO2 Infrared (IR) line list intensities is first validated by quantitative exploration of several dipole moment surfaces (DMSs) and partition sum convergence. The DMSs are computed with several of Dunning's correlation-consistent basis sets and their vibrational dependence are compared to the empirical model derived from Stark effect experiments reported by D. Patel, D. Margolese, and T.R. Dyke [J. Chem. Phys. 70, 2740 (1979)]. The effective dipole deviations from the DMS adopted in the Ames IR lists is 0.2–0.4% for vibrational states up to 3ν3. The vibrational dependence of the dipole moment is also in good agreement, except for nν1. Partition sum convergence at 296 K is confirmed by new calculations with rotational quantum number J up to 150 and upper state E’ up to 8000 cm−1. The isotopologue consistency of the Ames IR line lists is superior relative to the regular Effective Hamiltonian (EH) models and Effective Dipole Moment (EDM) models. The ν1 + ν2 and ν2 + ν3 intensity consistency check reveals the recently reported experimental intensities need significant improvement or re-analysis. After the accuracy, convergence, and isotopologue consistency have been confirmed, the theoretical Ames-296K intensities are combined with the experimental line positions or EH models that experimental spectroscopists published after 2009. Three high-resolution IR line sets are reported for the 32/33/34S16O2, 32S18O2 and 16O32S18O isotopologues: (1) the “New Lines Sets” include experimentally measured line positions; (2) the “Expanded Line Sets” include possible transitions among new rovibrational levels assigned in experiments and ground state (GS) levels predicted by reliable EH models; (3) the “Ames + MARVEL Sets” include possible transitions among all those levels reported in a recent MARVEL analysis. [Tobias et al, JQSRT 208, 152 (2018)]. Compared to the limited data in High-resolution TRANsmission molecular absorption database (HITRAN), these line sets have significantly improved the data coverage up to 4000 cm−1. Some missing bands can be traced to the unpublished experimental data. The isotopologue consistency of these line sets will help identify the uncertainties and defects in the experimental EH and EDM models. These line sets are good candidates for the next HITRAN update, if line shape parameters are available. The line sets can be downloaded from supplementary files or from the Ames Molecular Spectroscopic Database at http://huang.seti.org .
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- 2019
17. A collaborative 14NH3 IR spectroscopic analysis at 6000 cm−1
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Xinchuan Huang (黄新川), Keeyoon Sung, Geoffrey C. Toon, David W. Schwenke, and Timothy J. Lee
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Radiation ,Spectroscopy ,Atomic and Molecular Physics, and Optics - Published
- 2022
18. The First Mid-Infrared Detection of HNC in the Interstellar Medium: Probing the Extreme Environment Towards the Orion Hot Core
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Naseem Rangwala, Sean W. J. Colgan, Kinsuk Acharyya, Sarah Nickerson, Curtis DeWitt, Ryan C. Fortenberry, Eric Herbst, Xinchuan Huang, Maria Drozdovskaya, and Timothy J. Lee
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Physics ,Infrared astronomy ,010504 meteorology & atmospheric sciences ,530 Physics ,Star formation ,520 Astronomy ,Mid infrared ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Molecular spectroscopy ,01 natural sciences ,Astrophysics - Astrophysics of Galaxies ,Core (optical fiber) ,Interstellar medium ,13. Climate action ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,0103 physical sciences ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences - Abstract
We present the first mid-infrared (MIR) detections of HNC and H13CN in the interstellar medium, and numerous, resolved HCN rovibrational transitions. Our observations span 12.8 to 22.9 micron towards the hot core Orion IRc2, obtained with the Echelon-Cross-Echelle Spectrograph aboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). Exceptional, ~5 km/s, resolution distinguishes individual rovibrational transitions of the HNC and HCN P, Q, and R branches; and the H13CN R branch. This allows direct measurement of the species' excitation temperatures, column densities, and relative abundances. HNC and H13CN exhibit a local standard rest velocity of -7 km/s that may be associated with an outflow from nearby radio source I and an excitation temperature of about 100 K. We resolve two velocity components for HCN, the primary component also being at -7 km/s with temperature 165 K. The hottest component, which had never before been observed, is at 1 km/s with temperature 309 K. This is the closest component to the hot core's centre measured to date. The derived 12C/13C=13 is below expectation for Orion's Galactocentric distance, but the derived HCN/HNC=72 is expected for this extreme environment. Compared to previous sub-mm and mm observations, our SOFIA line survey of this region shows that the resolved MIR molecular transitions are probing a distinct physical component and isolating the chemistry closest to the hot core., 20 pages, 6 figures, submitted to ApJ, comments welcome
- Published
- 2020
19. The anharmonic quartic force field infrared spectra of hydrogenated and methylated PAHs
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Timothy J. Lee, Elena Maltseva, Alexander G. G. M. Tielens, Cameron J. Mackie, Alessandra Candian, Xinchuan Huang, Annemieke Petrignani, Wybren Jan Buma, Jos Oomens, and Molecular Spectroscopy (HIMS, FNWI)
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Physics ,Molecular Structure and Dynamics ,010304 chemical physics ,Molecular and Biophysics ,Anharmonicity ,Matrix isolation ,General Physics and Astronomy ,Infrared spectroscopy ,01 natural sciences ,Molecular physics ,Force field (chemistry) ,Spectral line ,Interstellar medium ,13. Climate action ,Quartic function ,0103 physical sciences ,Harmonic ,Physical and Theoretical Chemistry ,010303 astronomy & astrophysics ,GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries) - Abstract
Polycyclic aromatic hydrocarbons (PAHs) have been shown to be ubiquitous in a large variety of distinct astrophysical environments and are therefore of great interest to astronomers. The majority of these findings are based on theoretically predicted spectra, which make use of scaled DFT harmonic frequencies for band positions and the double harmonic approximation for intensities. However, these approximations have been shown to fail at predicting high-resolution gas-phase infrared spectra accurately, especially in the CH-stretching region (2950–3150 cm−1, 3 μm). This is particularly worrying for the subset of hydrogenated or methylated PAHs to which astronomers attribute the observed non-aromatic features that appear in the CH-stretching region of spectral observations of the interstellar medium (ISM). In our previous work, we presented the anharmonic theoretical spectra of three linear PAHs and five non-linear PAHs, demonstrating the importance of including anharmonicities into theoretical calculations. In this work we extend these techniques to two methylated PAHs (9-methylanthracene, and 9,10-dimethylanthracene) and four hydrogenated PAHs (9,10-dihydroanthracene, 9,10-dihydrophenanthrene, 1,2,3,4-tetrahydronaphthalene, and 1,2,3,6,7,8-hexahydropyrene) in order to better understand the aliphatic IR features of substituted PAHs. The theoretical spectra are compared with the spectra obtained under matrix isolation low-temperature conditions for the full vibrational fundamental range and under high-resolution, low-temperature gas-phase conditions for the CH-stretching region. Excellent agreement is observed between the theoretical and high-resolution experimental spectra with a deviation of 0.00% ± 0.17%, and changes to the spectra of PAHs upon methylation and hydrogenated are tracked accurately and explained.
- Published
- 2018
20. Total internal partition sums for 166 isotopologues of 51 molecules important in planetary atmospheres: Application to HITRAN2016 and beyond
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Eldon Lopes, Valery I. Perevalov, Tibor Furtenbacher, David W. Schwenke, Sergei N. Yurchenko, Aleksandra A. Kyuberis, Timothy J. Lee, Laurence S. Rothman, Roman V. Kochanov, Nikolai F. Zobov, Sergei A. Tashkun, Xinchuan Huang, Robert R. Gamache, Brian J. Drouin, Jonathan Tennyson, Oleg L. Polyansky, Christopher D. Roller, Attila G. Császár, and Iouli E. Gordon
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Physics ,Radiation ,010504 meteorology & atmospheric sciences ,Nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,0103 physical sciences ,Partition (number theory) ,Molecule ,Isotopologue ,Atomic physics ,010303 astronomy & astrophysics ,Spectroscopy ,0105 earth and related environmental sciences - Abstract
Total internal partition sums (TIPS) are reported for 166 isotopologues of 51 molecules important in planetary atmospheres. Molecules 1 to 50 are taken from the HITRAN2016 list, and, in some cases, additional isotopologues are considered for some of the molecules. Molecules 51–53 are C3H4, CH3, and CS2, respectively. TIPS are not reported for the O atom and CF4; thus, while there are 53 species in the list, data are reported for 51 molecules. The TIPS are determined by various methods from 1 K to a Tmax that ensures the TIPS reported have converged. These data are provided with HITRAN2016 and a new version of the TIPS code is available in both FORTRAN and python languages.
- Published
- 2017
21. Ames-2016 line lists for 13 isotopologues of CO2: Updates, consistency, and remaining issues
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Timothy J. Lee, David W. Schwenke, Richard Freedman, and Xinchuan Huang
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Radiation ,010504 meteorology & atmospheric sciences ,Rotational–vibrational spectroscopy ,Quantum number ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Spectral line ,Computational physics ,Nuclear magnetic resonance ,Consistency (statistics) ,0103 physical sciences ,Potential energy surface ,Isotopologue ,HITRAN ,010303 astronomy & astrophysics ,Spectroscopy ,0105 earth and related environmental sciences ,Mathematics ,Line (formation) - Abstract
A new 626-based Ames-2 PES refinement and Ames-2016 line lists for 13 CO2 isotopologues are reported. A consistent σRMS = ±0.02 cm−1 is established for hundreds of isotopologue band origins using the Ames-2 PES. Ames-2016 line lists are computed at 296 K, 1000 K and 4000 K using the Ames-2 PES and the same DMS-N2 dipole surface used previously, with J up to 150, E′ up to 24,000 cm−1 or 18,000 cm−1 and appropriate intensity cutoffs. The lists are compared to the CDSD-296, CDSD-4000 databases, UCL line lists, and a few recent highly accurate CO2 intensity measurements. Both agreements and discrepancies are discussed. Compared to the old Ames CO2 lists, the Ames-2016 line lists have line position deviations reduced by 50% or more, which consequently leads to more reliable intensities. The line shape parameters in the Ames-2016 line lists are predicted using the newly assigned conventional vibrational polyad quantum numbers for rovibrational levels below 12,000 cm−1 so the quality of the line shape parameters is similar to that of CDSD or HITRAN. This study further proves that a semi-empirically refined PES (Ames-1 and Ames-2) coupled with a high quality ab initio DMS (DMS-N2 and UCL) may generate IR predictions with consistent accuracy and is thus helpful in the analysis of laboratory spectra and simulations of various isotopologues. The Ames-2016 lists based on DMS-N2 have reached the ∼1% intensity prediction accuracy level for the recent 626 30013-00001 and 20013-00001 bands, but further quantification and improvements require sub-percent or sub-half-percent accurate experimental intensities. The inter-isotopologue consistency of the intensity prediction accuracies should have reached better than 1–3% for regular bands not affected by resonances. Since the Effective Dipole Models (EDM) in CDSD and HITRAN have 1–20% or even larger uncertainties, we show that the Ames lists can provide better alternative IR data for many hard-to-determine isotopologue bands. Comparison at 4000 K suggests that the Ames-4000 K 12C16O2 line list is reliable and consistent within the current cutoffs of J ≤ 150 and E′ ≤ 24,000 cm−1, but intensity contributions involving higher energy levels should not be omitted and future computations need to be converged up to at least 32,000 cm−1 or higher. The remaining issues are discussed regarding the source of energy level discrepancies, intensity underestimations by ∼50% for some weak bands, etc. and also future work.
- Published
- 2017
22. Towards completing the cyclopropenylidene cycle: rovibrational analysis of cyclic N3+, CNN, HCNN+, and CNC−
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Ryan C. Fortenberry, Timothy J. Lee, and Xinchuan Huang
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chemistry.chemical_classification ,Cyclopropenylidene ,010304 chemical physics ,General Physics and Astronomy ,Rotational–vibrational spectroscopy ,01 natural sciences ,Ion ,symbols.namesake ,chemistry.chemical_compound ,Dipole ,chemistry ,0103 physical sciences ,symbols ,Molecule ,Physical and Theoretical Chemistry ,Atomic physics ,Aromatic hydrocarbon ,Titan (rocket family) ,010303 astronomy & astrophysics - Abstract
The simple aromatic hydrocarbon, cyclopropenylidene (c-C3H2), is a known, naturally-occurring molecule. The question remains as to whether its isoelectronic, cyclic, fellow aromatics of c-N3+, c-CNN, HCNN+, and c-CNC− are as well. Each of these are exciting objects for observation of Titan, and the rotational constants and vibrational frequencies produced here will allow for remote sensing of Titan's atmosphere or other astrophysical or terrestrial sources. None of these four aromatic species are vibrationally strong absorbers/emitters, but the two ions, HCNN+ and c-CNC−, have dipole moments of greater than 3 D and 1 D, respectively, making them good targets for rotational spectroscopic observation. Each of these molecules is shown here to exhibit its own, unique vibrational properties, but the general trends put the vibrational behavior for corresponding fundamental modes within close ranges of one another, even producing nearly the same heavy atom, symmetric stretching frequencies for HCNN+ and c-C3H2 at 1600 cm−1. The c-N3+ cation is confirmed to be fairly unstable and has almost no intensity in its ν2 fundamental. Hence, it will likely remain difficult to characterize experimentally.
- Published
- 2017
23. IMPROVE THE PREDICTION ACCURACY OF ISOTOPOLOGUE MICROWAVE SPECTRA BY COMBINING AMES-296K SO2 IR LISTS WITH EXPERIMENTAL MODELS: A BENCHMARK STUDY
- Author
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Timothy J. Lee, David W. Schwenke, and Xinchuan Huang
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Materials science ,Far infrared spectroscopy ,Microwave spectra ,Benchmark (computing) ,Isotopologue ,Computational physics - Published
- 2018
24. Empirical infrared line lists for five SO2 isotopologues: 32/33/34/36S16O2 and 32S18O2
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David W. Schwenke, Timothy J. Lee, and Xinchuan Huang
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Physics ,Infrared ,Ab initio ,Rotational–vibrational spectroscopy ,Atomic and Molecular Physics, and Optics ,Line list ,Dipole ,Nuclear magnetic resonance ,Potential energy surface ,Isotopologue ,HITRAN ,Physical and Theoretical Chemistry ,Atomic physics ,Spectroscopy - Abstract
Using the latest published, empirically refined potential energy surface (PES) Ames-1 and purely ab initio CCSD(T)/aug-cc-pV(Q+d)Z dipole moment surface (DMS), we have computed infrared line lists for five symmetric isotopologues of sulfur dioxide: 32S16O2 (626), 33S16O2 (636), 34S16O2 (646), 36S16O2 (666), and 32S18O2 (828). The line lists are based on J = 0–80 rovibrational variational calculations with E′ ⩽ 8000 cm−1. The 34S16O2 and 33S16O2 line lists are compared to the experiment-based models in the HIgh-resolution TRANsmission molecular absorption database (HITRAN2012, http://www.cfa.harvard.edu/hitran/ ) and the Cologne Database for Molecular Spectroscopy, CDMS ( http://www.astro.uni-koeln.de/cdms/ ). The accuracy for computed 646 band origins is similar to what has been reported for the main isotopologue, i.e. 0.01–0.03 cm−1 for bands up to 5500 cm−1. For rovibrational transitions, the 646 line position and intensity deviation patterns are much simpler and more self-consistent than those of the main isotopologue 626. The discrepancies are mainly found for higher Ka/J transitions. 626 and 646 exhibit comparable line position and intensity agreement for lower Ka/J transitions. The line position deviations for the 636 purely rotational band are parallel to those of 626 and 646, while its line intensity deviations do not show branching patterns as we found in the 626 and 646 cases. Predictions for the other minor isotopologues are expected to exhibit similar accuracy. These line lists are accurate enough to provide alternatives for missing bands of 626 and the minor isotopologues. It may significantly facilitate the laboratory spectroscopic measurement and analysis, as well as to identify these isotopologues in various astrophysical environments.
- Published
- 2015
25. Reliable infrared line lists for 13 CO2 isotopologues up to E′=18,000cm−1 and 1500K, with line shape parameters
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Timothy J. Lee, David W. Schwenke, Richard Freedman, Xinchuan Huang, and Robert R. Gamache
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Physics ,Radiation ,biology ,Infrared ,Zero-point energy ,Venus ,Mars Exploration Program ,biology.organism_classification ,Atomic and Molecular Physics, and Optics ,Computational physics ,Position (vector) ,Isotopologue ,HITRAN ,Line (text file) ,Spectroscopy ,Remote sensing - Abstract
Reliable infrared (IR) line lists are reported for the 13 isotopologues of carbon dioxide in HITRAN notation: 626, 636, 628, 627, 828, 727, 827, 638, 637, 737, 838, 738, and 646. Three IR lists are available for each istotopologue: a complete list at 296 K, a reduced-size list at 296 K, plus a reduced-size list at 1000 K. They are denoted Ames-296K, Ames-296K.reduced and Ames-1000K.reduced. With J up to 150, and energy up to 18,000 cm−1 above the zero point energy, these lists are expected to cover the temperature range up to 1500 K. Line shape parameters including temperature dependence are calculated and reported for four temperature ranges: Mars, Earth, Venus, and Hotter (700–2000 K). Comparisons are made against the available transition data in the HITRAN2012 models. Line position accuracy for most transitions up to 10,000–13,000 cm−1 is better than 0.03–0.05 cm−1. Computed transition intensities agree well with most HITRAN data but there exist suspicious exceptions for isotopologues. These line lists will expedite CO2 IR experimental data analysis and provide the scientific community with trustworthy alternatives for unknown IR bands. These line lists may be combined with existing experimental databases to facilitate the analysis of future laboratory experiments or astronomical observations.
- Published
- 2014
26. High Spectral Resolution SOFIA/EXES Observations of C2H2 towards Orion-IRc2
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Matthew J. Richter, Timothy J. Lee, Xinchuan Huang, Mark E. McKelvey, Naseem Rangwala, Romane Le Gal, Adwin Boogert, Eric Herbst, Sean W. J. Colgan, Kinsuk Acharyya, and C. DeWitt
- Subjects
Physics ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,0103 physical sciences ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Spectral resolution ,010306 general physics ,010303 astronomy & astrophysics ,01 natural sciences ,Astrophysics - Astrophysics of Galaxies - Abstract
We present high-spectral resolution observations from 12.96 - 13.33 microns towards Orion IRc2 using the mid-infrared spectrograph, EXES, on SOFIA. These observations probe the physical and chemical conditions of the Orion hot core, which is sampled by a bright, compact, mid-infrared background continuum source in the region, IRc2. All ten of the rovibrational C2H2 transitions expected in our spectral coverage, are detected with high S/N, yielding continuous coverage of the R-branch lines from J=9-8 to J=18-17, including both ortho and para species. Eight of these rovibrational transitions are newly reported detections. The isotopologue, 13CCH2, is clearly detected with high signal-to-noise. This enabled a direct measurement of the 12C/13C isotopic ratio for the Orion hot core of 14 +/- 1 and an estimated maximum value of 21. We also detected several HCN rovibrational lines. The ortho and para C2H2 ladders are clearly separate and tracing two different temperatures, 226 K and 164 K, respectively, with a non-equilibrium ortho to para ratio (OPR) of 1.7 +\- 0.1. Additionally, the ortho and para V_LSR values differ by about 1.8 +/- 0.2 km/s, while, the mean line widths differ by 0.7 +/- 0.2 km/s, suggesting that these species are not uniformly mixed along the line of sight to IRc2. We propose that the abnormally low C2H2 OPR could be a remnant from an earlier, colder phase, before the density enhancement (now the hot core) was impacted by shocks generated from an explosive event 500 yrs ago., accepted for publication in The Astrophysical Journal
- Published
- 2017
27. Towards completing the cyclopropenylidene cycle: rovibrational analysis of cyclic N
- Author
-
Ryan C, Fortenberry, Timothy J, Lee, and Xinchuan, Huang
- Abstract
The simple aromatic hydrocarbon, cyclopropenylidene (c-C
- Published
- 2017
28. Semi-empirical 12C16O2 IR line lists for simulations up to 1500K and 20,000cm−1
- Author
-
S.A. Tashkun, Timothy J. Lee, Richard Freedman, Xinchuan Huang, and David W. Schwenke
- Subjects
Physics ,Radiation ,Ab initio ,Rotational–vibrational spectroscopy ,Atomic and Molecular Physics, and Optics ,Computational physics ,Moment (mathematics) ,Dipole ,Nuclear magnetic resonance ,Potential energy surface ,Range (statistics) ,HITRAN ,Spectroscopy ,Line (formation) - Abstract
New semi-empirical Infrared (IR) line lists for 12C16O2, Ames-296 K and Ames-1000 K, have been computed using a newly updated ab initio CCSD(T)/aug-cc-pVQZ dipole moment surface (denoted DMS-N2) and an empirically refined potential energy surface (Ames-1). J=0–150 rovibrational levels are computed up to 30,000 cm−1, and related transitions are cut off at 1E−42 cm molecule−1 (296 K) and 1E−36 cm molecule−1 (1000 K). These are the first line lists available to cover reliably the energy region as high as ~20,000 cm−1. Recent experimental data at 1.1 μm has confirmed the predicted intensities for the 50013-00001 and 50014-00001 band transitions have better than 90% agreement. Comparisons are made against the Wattson 750 K line list and HITEMP/HITRAN at 300 K, 500 K, 725 K, 1000 K, 1500 K, 2000 K and 3000 K. The temperature dependence and accuracy of the new Ames-296 K/1000 K line lists are investigated and we claim both line lists are capable of providing reliable opacities up to 18,000–23,000 cm−1, while the highest applicable wavenumber range drops as T rises. We suggest caution is used for T>1000 K simulations. Comparison to recent experiments at 1000 K, 1550 K and 1773 K shows that the Ames-1000 K line list and HITEMP perform similarly in the 3200–3800 cm−1 and 4600–5200 cm−1 ranges. In the 2000–2100 cm−1 range, Ames-1000 K yields better agreement relative to experiment. Existing problems and possible future solutions in the new Ames-296 K/1000 K line lists for line positions and intensities are also discussed.
- Published
- 2013
29. On the use of quartic force fields in variational calculations
- Author
-
Walter Thiel, Ryan C. Fortenberry, Andrey Yachmenev, Xinchuan Huang, and Timothy J. Lee
- Subjects
Physics ,General Physics and Astronomy ,Rotational–vibrational spectroscopy ,Potential energy ,Symmetry (physics) ,symbols.namesake ,Classical mechanics ,Quartic function ,Harmonics ,Quantum mechanics ,Taylor series ,symbols ,Sine ,Physical and Theoretical Chemistry ,Scaling - Abstract
Quartic force fields (QFFs) have been shown to be one of the most effective ways to efficiently compute vibrational frequencies for small molecules. In this letter we discuss how the simple-internal or bond-length bond-angle (BLBA) coordinates can be transformed into Morse-cosine (-sine) coordinates which produce potential energy surfaces from QFFs that possess proper limiting behavior and can describe the vibrational (or rovibrational) energy levels of an arbitrary molecular system to 5 cm −1 or better compared to experiment. We investigate parameter scaling in the Morse coordinate, symmetry considerations, and examples of transformed QFFs making use of the MULTIMODE, TROVE, and VTET variational vibrational methods.
- Published
- 2013
30. Dipole Surface and Infrared Intensities for the cis- and trans-HOCO and DOCO Radicals
- Author
-
Joseph S. Francisco, Xinchuan Huang, Ryan C. Fortenberry, Timothy J. Lee, Joel M. Bowman, Yimin Wang, and T. Daniel Crawford
- Subjects
Dipole ,Coupled cluster ,Deuterium ,Computational chemistry ,Chemistry ,Infrared ,Isotopologue ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Configuration interaction ,Molecular physics ,Conformational isomerism ,Spectral line - Abstract
The vibrational spectra for the HOCO radical in both of its conformers and deuterated isotopologues are shown here for the first time. Building on previous work with coupled cluster quartic force fields (QFFs) in the computation of the fundamental vibrational frequencies for both cis- and trans-HOCO, coupled cluster dipole surfaces are now provided for both HOCO conformers and their corresponding deuterated isotopologues. These surfaces and subsequent vibrational configuration interaction (VCI) computations produce the intensities of transitions into vibrational states including the fundamentals, overtones, and first few combination bands of less than 4000 cm(-1), slightly beyond the O-H stretch. Simulated spectra with an artificial full width at half-maximum broadening of 10 cm(-1) are also provided in order to aid in the characterization of HOCO's vibrational frequencies and to assist detection in various laboratory or astronomical observations.
- Published
- 2012
31. The 1 3A′ HCN and 1 3A′ HCO+ Vibrational Frequencies and Spectroscopic Constants from Quartic Force Fields
- Author
-
Timothy J. Lee, Xinchuan Huang, Ryan C. Fortenberry, and T. Daniel Crawford
- Subjects
Work (thermodynamics) ,Coupled cluster ,Chemistry ,Quartic function ,Bent molecular geometry ,Molecule ,Physical and Theoretical Chemistry ,Atomic physics - Abstract
Building on previous studies involving coupled cluster quartic force fields for the description of spectroscopic constants and vibrational frequencies of astronomically relevant molecules, this work applies the same techniques to the elucidation of such properties for the bent 1 (3)A' state of HCN and the isoelectronic 1 (3)A' HCO(+). Core correlation is treated both by explicit means and as a correction. Each approach gives closely comparable spectroscopic constants and vibrational frequencies once more, indicating that the composite method is a viable and less costly alternative. We are providing fundamental vibrational frequencies for these systems where agreement with experiment in previous studies has been within 4 cm(-1) or better. Frequencies for the first overtones and combination bands as well as various spectroscopic constants are also reported.
- Published
- 2012
32. LIGHT ON THE 3 μm EMISSION BAND FROM SPACE WITH MOLECULAR BEAM SPECTROSCOPY
- Author
-
Wybren Jan Buma, Xander Tielens, Cameron J. Mackie, Elena Maltseva, Annemieke Petrignani, Alessandra Candian, Jos Oomens, Timothy J. Lee, and Xinchuan Huang
- Subjects
Physics ,Emission band ,Optics ,business.industry ,Molecular-beam spectroscopy ,Optoelectronics ,Space (mathematics) ,business - Published
- 2016
33. ExoMol molecular line lists - XIV: The rotation-vibration spectrum of hot SO$_2$
- Author
-
Timothy J. Lee, Xinchuan Huang, Sergei N. Yurchenko, Sønnik Clausen, Jonathan Tennyson, David W. Schwenke, Daniel S. Underwood, and Alexander Fateev
- Subjects
Opacity ,Infrared spectroscopy ,FOS: Physical sciences ,Venus ,Astrophysics ,01 natural sciences ,chemistry.chemical_compound ,0103 physical sciences ,miscellaneous [Astronomical data bases] ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Physics ,Supplementary data ,Earth and Planetary Astrophysics (astro-ph.EP) ,010304 chemical physics ,biology ,Molecular line ,Molecular data ,Astronomy and Astrophysics ,biology.organism_classification ,Vibration ,Wavelength ,chemistry ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Sulfur trioxide ,atmospheres [Planets and satellites] ,Atomic physics ,Astrophysics - Earth and Planetary Astrophysics - Abstract
Sulphur dioxide is well-known in the atmospheres of planets and satellites, where its presence is often associated with volcanism, and in circumstellar envelopes of young and evolved stars as well as the interstellar medium. This work presents a line list of 1.3 billion $^{32}$S$^{16}$O$_2$ vibration-rotation transitions computed using an empirically-adjusted potential energy surface and an ab initio dipole moment surface. The list gives complete coverage up to 8000 cm$^{-1}$ (wavelengths longer than 1.25 $\mu$m) for temperatures below 2000 K. Infrared absorption cross sections are recorded at 300 and 500 C are used to validated the resulting ExoAmes line list. The line list is made available in electronic form as supplementary data to this article and at www.exomol.com., Comment: Submitted to MNRAS
- Published
- 2016
- Full Text
- View/download PDF
34. Fundamental Vibrational Frequencies and Spectroscopic Constants of HOCS+, HSCO+, and Isotopologues via Quartic Force Fields
- Author
-
Timothy J. Lee, Ryan C. Fortenberry, Xinchuan Huang, T. Daniel Crawford, and Joseph S. Francisco
- Subjects
Chemistry ,Rotational–vibrational spectroscopy ,Configuration interaction ,Molecular physics ,Spectral line ,Interstellar medium ,Vibrational partition function ,Quartic function ,Physics::Atomic and Molecular Clusters ,Molecule ,Isotopologue ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Atomic physics - Abstract
Besides the ν(1) O-H stretching mode at 3435 cm(-1) for HOCS(+), the fundamental vibrational frequencies for this cation and its HSCO(+) isomer have not been determined experimentally. Because these systems are analogues to HOCO(+), a detected interstellar molecule, and are believed to play an important role in reactions of OCS, which has also been detected in the interstellar medium, these cations are of importance to interstellar chemistry and reaction surface studies. This work provides the fundamental vibrational frequencies and spectroscopic constants computed with vibrational perturbation theory (VPT) at second order and the vibrational configuration interaction (VCI) method conjoined with the most accurate quartic force field (QFF) applied to date for these systems. Our computations match experiment to better than 2 cm(-1) for the known O-H stretch. Additionally, there is strong agreement in the prediction of the fundamentals across methods and choices of QFFs. The consistency in the computations and the correspondence for the known mode should give accurate reference data for the rovibrational spectra of these cations and their singly substituted isotopologues for D, (18)O, and (34)S.
- Published
- 2012
35. Extended line positions, intensities, empirical lower state energies and quantum assignments of NH3 from 6300 to 7000cm−1
- Author
-
Timothy J. Lee, Xinchuan Huang, David W. Schwenke, Stephen L. Coy, Linda R. Brown, Kevin K. Lehmann, and Keeyoon Sung
- Subjects
Physics ,Radiation ,Observatory ,Planet ,Ab initio quantum chemistry methods ,Near-infrared spectroscopy ,Brown dwarf ,Atomic physics ,Ground state ,Spectroscopy ,Atomic and Molecular Physics, and Optics ,Spectral line ,Line (formation) - Abstract
Nearly 4800 features of ammonia between 6300 and 7000 cm−1 with intensities ≥4×10−24 cm−1/(molecule·cm−2) at 296 K were measured using 16 pure NH3 spectra recorded at various temperatures (296–185 K) with the McMath–Pierce Fourier Transform Spectrometer at Kitt Peak National Observatory, AZ. The line positions and intensities were retrieved by fitting individual spectra based on a Voigt line shape profile and then averaging the values to form the experimental linelist. The integrated intensity of the region was 4.68×10−19 cm−1/(molecule·cm−2) at 296 K. Empirical lower state energies were also estimated for 3567 absorption line features using line intensities retrieved from 10 spectra recorded at gas temperature between 185 and 233 K. Finally, using Ground State Combination Differences (GSCDs) and the empirical lower state energy estimates, the quantum assignments were determined for 1096 transitions in the room temperature linelist, along with empirical upper state energies for 434 levels. The assignments correspond to seven vibrational states, as confirmed from recent ab initio calculations. The resulting composite database of 14NH3 line parameters will provide experimental constraints to ab initio calculations and support remote sensing of gaseous bodies including the atmospheres of Earth, (exo)planets, brown dwarfs, and other astrophysical environments.
- Published
- 2012
36. Ab-Initio-Based Potential Energy Surfaces for Complex Molecules and Molecular Complexes
- Author
-
Joel M. Bowman, Benjamin C. Shepler, Amit R. Sharma, Stuart Carter, Chao Chen, Yimin Wang, Gábor Czakó, Bastiaan J. Braams, Eugene Kamarchik, Xinchuan Huang, Bina Fu, and Z. Xie
- Subjects
Chemistry ,Potential energy surface ,Ab initio ,Molecule ,General Materials Science ,Electronic structure ,Physical and Theoretical Chemistry ,Molecular physics ,Potential energy - Abstract
The Born−Oppenheimer potential energy surface(s) underlies theoretical and computational chemistry (whether one considers a single or multiply coupled surfaces). The recent progress in representing these surfaces, rigorously obtained from electronic structure calculations, is the focus of this Perspective. Examples of potentials of complex molecules, namely, CH3CHO, CH5+, and H5+, and molecular complexes, namely, water clusters, are given.
- Published
- 2010
37. High-resolution IR absorption spectroscopy of polycyclic aromatic hydrocarbons in the 3 μm region: role of hydrogenation and alkylation
- Author
-
Elena Maltseva, Timothy J. Lee, Jos Oomens, Cameron J. Mackie, Alexander G. G. M. Tielens, Wybren Jan Buma, Alessandra Candian, Annemieke Petrignani, Xinchuan Huang, and Molecular Spectroscopy (HIMS, FNWI)
- Subjects
FELIX Molecular Structure and Dynamics ,chemistry.chemical_classification ,Physics ,Astrochemistry ,010304 chemical physics ,Absorption spectroscopy ,Anharmonicity ,Analytical chemistry ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Alkylation ,Mass spectrometry ,Astrophysics - Astrophysics of Galaxies ,01 natural sciences ,chemistry ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,0103 physical sciences ,Emission spectrum ,Spectroscopy ,010303 astronomy & astrophysics ,Alkyl - Abstract
Aims. We aim to elucidate the spectral changes in the 3 micron region that result from chemical changes in the molecular periphery of polycyclic aromatic hydrocarbons (PAHs) with extra hydrogens (H-PAHs) and methyl groups (Me-PAHs). Methods. Advanced laser spectroscopic techniques combined with mass spectrometry were applied on supersonically cooled 1,2,3,4-tetrahydronaphthalene, 9,10-dihydroanthracene, 9,10-dihydrophenathrene, 1,2,3,6,7,8-hexahydropyrene, 9-methylanthracene, and 9,10-dimethylanthracene, allowing us to record mass-selective and conformationally selective absorption spectra of the aromatic, aliphatic, and alkyl CH-stretches in the 3.175-3.636 micron region with laser-limited resolution. We compared the experimental absorption spectra with standard harmonic calculations and with second-order vibrational perturbation theory anharmonic calculations that use the SPECTRO program for treating resonances. Results. We show that anharmonicity plays an important if not dominant role, affecting not only aromatic, but also aliphatic and alkyl CH-stretch vibrations. The experimental high-resolution data lead to the conclusion that the variation in Me- and H-PAHs composition might well account for the observed variations in the 3 micron emission spectra of carbon-rich and star-forming regions. Our laboratory studies also suggest that heavily hydrogenated PAHs form a significant fraction of the carriers of IR emission in regions in which an anomalously strong 3 micron plateau is observed., Comment: 13 pages, 8 Figures, 1 table, accepted for publication in A&A
- Published
- 2018
38. The effect of approximating some molecular integrals in coupled-cluster calculations: fundamental frequencies and rovibrational spectroscopic constants for isotopologues of cyclopropenylidene
- Author
-
Christopher E. Dateo, Xinchuan Huang, and Timothy J. Lee
- Subjects
Physics ,Cyclopropenylidene ,Biophysics ,Rotational–vibrational spectroscopy ,Condensed Matter Physics ,Force field (chemistry) ,chemistry.chemical_compound ,Coupled cluster ,chemistry ,Quantum mechanics ,Quartic function ,Isotopologue ,Molecular orbital ,Physical and Theoretical Chemistry ,Molecular Biology ,Basis set - Abstract
The effect of approximating the three- and four-virtual molecular orbital integrals in single and double coupled-cluster theory including a perturbational correction for connected triple excitations [CCSD(T)] is investigated for the calculation of higher-order properties, specifically the calculation of a molecular quartic force field and spectroscopic constants. The approach was proposed previously, but investigated for only second- and lower-order properties. It is shown that the conclusions reached previously are essentially unchanged on moving to higher-order properties. That is, approximating the selected integrals has essentially no effect on the accuracy of CCSD(T) calculations, and the error due to approximating integrals is much smaller than the residual error due to one-particle basis set deficiencies. The advantage of this approach is that it significantly reduces the amount of data needed to perform CCSD(T) calculations, thereby reducing computational requirements associated with input/output ...
- Published
- 2009
39. Comparison of quantum, classical, and ring-polymer molecular dynamics infra-red spectra of Cl−(H2O) and H+(H2O)2
- Author
-
Scott Habershon, Xinchuan Huang, and Joel M. Bowman
- Subjects
chemistry.chemical_classification ,Molecular dynamics ,Chemistry ,Infrared ,Ab initio ,General Physics and Astronomy ,Physical chemistry ,Polymer ,Physical and Theoretical Chemistry ,Ring (chemistry) ,Quantum ,Astrophysics::Galaxy Astrophysics ,Spectral line - Abstract
We present a comparison of the infra-red spectra of Cl-(H2O) and H+(H2O)(2) obtained with classical and ring-polymer molecular dynamics with previous quantum calculations. Full-dimensional ab initio-based potential and dipole-moment surfaces are used in these calculations. (C) 2007 Elsevier B.V. All rights reserved.
- Published
- 2008
40. SO2 and CO2 IR line lists for atmospheric modeling on Venus and Exoplanets
- Author
-
Timothy J. Lee, Xinchuan Huang, and David W. Schwenke
- Subjects
Physics ,Line list ,biology ,Space and Planetary Science ,Infrared ,Astronomy ,Astronomy and Astrophysics ,Venus ,Observable ,Isotopologue ,Atmospheric model ,biology.organism_classification ,Exoplanet - Abstract
Highly accurate IR line lists are ready for 13 CO2 isotopologues and 7 SO2 isotopologues. Ames-296K IR lists carry 0.01 - 0.03 cm−1 accuracy up to 13,000 cm−1 for CO2 and 5500 cm−1 for SO2, and 90–95% intensity agreement for most observable bands. Good for atmospheric modeling on Venus and Exoplanets.
- Published
- 2015
41. RELIABLE IR LINE LISTS FOR SO2 AND CO2 ISOTOPOLOGUES COMPUTED FOR ATMOSPHERIC MODELING ON VENUS AND EXOPLANETS
- Author
-
Xinchuan Huang, Timothy J. Lee, David W. Schwenke, and Robert R. Gamache
- Subjects
Line list ,Geography ,biology ,Venus ,Isotopologue ,Atmospheric model ,biology.organism_classification ,Exoplanet ,Astrobiology - Published
- 2015
42. The anharmonic quartic force field infrared spectra of three polycyclic aromatic hydrocarbons: naphthalene, anthracene, and tetracene
- Author
-
Elena Maltseva, Wybren Jan Buma, Cameron J. Mackie, Xinchuan Huang, Jos Oomens, Alessandra Candian, Annemieke Petrignani, Alexander G. G. M. Tielens, Timothy J. Lee, and Molecular Spectroscopy (HIMS, FNWI)
- Subjects
Anthracene ,010304 chemical physics ,Molecular Structure and Dynamics ,Infrared ,Anharmonicity ,Matrix isolation ,Analytical chemistry ,General Physics and Astronomy ,Infrared spectroscopy ,01 natural sciences ,Molecular physics ,Spectral line ,chemistry.chemical_compound ,Tetracene ,chemistry ,0103 physical sciences ,Fermi resonance ,Physical and Theoretical Chemistry ,010303 astronomy & astrophysics ,Hardware_REGISTER-TRANSFER-LEVELIMPLEMENTATION ,Astrophysics::Galaxy Astrophysics - Abstract
Current efforts to characterize and study interstellar polycyclic aromatic hydrocarbons(PAHs) rely heavily on theoretically predicted infrared (IR) spectra. Generally, such studies use the scaled harmonic frequencies for band positions and double harmonic approximation for intensities of species, and then compare these calculated spectra with experimental spectra obtained under matrix isolation conditions. High-resolution gas-phase experimental spectroscopic studies have recently revealed that the double harmonic approximation is not sufficient for reliable spectra prediction. In this paper, we present the anharmonic theoretical spectra of three PAHs: naphthalene, anthracene, and tetracene, computed with a locally modified version of the SPECTRO program using Cartesian derivatives transformed from Gaussian 09 normal coordinate force constants. Proper treatments of Fermi resonances lead to an impressive improvement on the agreement between the observed and theoretical spectra, especially in the C–H stretching region. All major IR absorption features in the full-scale matrix-isolated spectra, the high-temperature gas-phase spectra, and the most recent high-resolution gas-phase spectra obtained under supersonically cooled molecular beam conditions in the CH-stretching region are assigned.
- Published
- 2015
43. Linear transformation of anharmonic molecular force constants between normal and Cartesian coordinates
- Author
-
Timothy J. Lee, Cameron J. Mackie, Alessandra Candian, Xinchuan Huang, and Alexander G. G. M. Tielens
- Subjects
Hessian matrix ,010304 chemical physics ,Log-polar coordinates ,General Physics and Astronomy ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,law.invention ,symbols.namesake ,Classical mechanics ,Transformation (function) ,Orthogonal coordinates ,law ,Quartic function ,0103 physical sciences ,symbols ,Normal coordinates ,Cartesian coordinate system ,Physical and Theoretical Chemistry ,Eigenvalues and eigenvectors ,Mathematics - Abstract
A full derivation of the analytic transformation of the quadratic, cubic, and quartic force constants from normal coordinates to Cartesian coordinates is given. Previous attempts at this transformation have resulted in non-linear transformations; however, for the first time, a simple linear transformation is presented here. Two different approaches have been formulated and implemented, one of which does not require prior knowledge of the translation-rotation eigenvectors from diagonalization of the Hessian matrix. The validity of this method is tested using two molecules H2O and c-C3H2D+
- Published
- 2015
44. High-resolution IR Absorption Spectroscopy of Polycyclic Aromatic Hydrocarbons: The Realm of Anharmonicity
- Author
-
Xinchuan Huang, Jos Oomens, Alexander G. G. M. Tielens, Annemieke Petrignani, Cameron J. Mackie, Elena Maltseva, Wybren Jan Buma, Timothy J. Lee, Alessandra Candian, and Molecular Spectroscopy (HIMS, FNWI)
- Subjects
spectroscopy ,Infrared ,Infrared spectroscopy ,FOS: Physical sciences ,Astrophysics ,Molecular physics ,Spectral line ,chemistry.chemical_compound ,PAHs ,Physics - Chemical Physics ,11. Sustainability ,FELIX ,Physics::Chemical Physics ,Spectroscopy ,GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries) ,Astrophysics::Galaxy Astrophysics ,astrochemistry: molecules ,Naphthalene ,Physics ,Chemical Physics (physics.chem-ph) ,Anthracene ,Molecular Structure and Dynamics ,Anharmonicity ,Astronomy and Astrophysics ,Astrophysics - Astrophysics of Galaxies ,3. Good health ,Tetracene ,chemistry ,13. Climate action ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,line identification - Abstract
We report on an experimental and theoretical investigation of the importance of anharmonicity in the 3 micron CH stretching region of Polycyclic Aromatic Hydrocarbon (PAH) molecules. We present mass-resolved, high-resolution spectra of the gas-phase cold (~4K) linear PAH molecules naphthalene, anthracene, and tetracene. The measured IR spectra show a surprisingly high number of strong vibrational bands. For naphthalene, the observed bands are well separated and limited by the rotational contour, revealing the band symmetries. Comparisons are made to the harmonic and anharmonic approaches of the widely used Gaussian software. We also present calculated spectra of these acenes using the computational program SPECTRO, providing anharmonic predictions enhanced with a Fermi-resonance treatment that utilises intensity redistribution. We demonstrate that the anharmonicity of the investigated acenes is strong, dominated by Fermi resonances between the fundamental and double combination modes, with triple combination bands as possible candidates to resolve remaining discrepancies. The anharmonic spectra as calculated with SPECTRO lead to predictions of the main modes that fall within 0.5% of the experimental frequencies. The implications for the Aromatic Infrared Bands, specifically the 3 micron band are discussed., Comment: v.2 (02/11/15) Updated: references, figures and affiliation
- Published
- 2015
45. 10 Buddhist Interaction between China and Korean Peninsula during the Sui and Tang Dynasties: A Survey of Korean Monk Visitors in China
- Author
-
Xinchuan Huang
- Subjects
geography ,geography.geographical_feature_category ,Peninsula ,Buddhism ,Ancient history ,China ,Asian studies - Published
- 2015
46. Tests of MULTIMODE calculations of rovibrational energies of CH4
- Author
-
Joel M. Bowman, Stuart Carter, Xinchuan Huang, and Jiayan Wu
- Subjects
Physics ,Multi-mode optical fiber ,Total angular momentum quantum number ,Angular momentum coupling ,Mode coupling ,Ab initio ,General Physics and Astronomy ,Rotational–vibrational spectroscopy ,Physical and Theoretical Chemistry ,Atomic physics ,Force field (chemistry) - Abstract
We report variational calculations of rovibrational energies of CH 4 using the code MULTIMODE and an ab initio force field of Schwenke and Partridge. The systematic convergence of the energies with respect to the level of mode coupling is presented. Converged vibrational energies calculated using the five-mode representation of the potential for zero total angular momentum are compared with previous, benchmark calculations based on Radau coordinates using this force field for zero total angular momentum and for J = 1. Very good agreement with the previous benchmark calculations is found.
- Published
- 2006
47. The determination of molecular properties from MULTIMODE with an application to the calculation of Franck–Condon factors for photoionization of CF3to
- Author
-
Lawrence B. Harding, Xinchuan Huang, Stuart Carter, and Joel M. Bowman
- Subjects
Multi-mode optical fiber ,Chemistry ,Biophysics ,Ab initio ,Photoionization ,Rotational–vibrational spectroscopy ,Condensed Matter Physics ,Potential energy surface ,Physics::Atomic and Molecular Clusters ,Code (cryptography) ,Physics::Atomic Physics ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Atomic physics ,Wave function ,Molecular Biology - Abstract
Extensions to the code MULTIMODE to obtain rovibrational wave functions and properties are described. An application of these new capabilities is made to a calculation of the Franck–Condon factors for photoionization of CF3 to CF . These calculations make use of a new, full-dimensional ab initio potential energy surface, which is also described here.
- Published
- 2006
48. Quantum Deconstruction of the Infrared Spectrum of CH 5 +
- Author
-
Chandra Savage, Joel M. Bowman, Lindsay M. Johnson, Feng Dong, Xinchuan Huang, Anne B. McCoy, and David J. Nesbitt
- Subjects
Dipole ,Multidisciplinary ,Nuclear magnetic resonance ,Infrared ,Chemistry ,Molecular vibration ,Ab initio ,Infrared spectroscopy ,Spectral bands ,Potential energy ,Molecular physics ,Spectral line - Abstract
We present two quantum calculations of the infrared spectrum of protonated methane (CH 5 + ) using full-dimensional, ab initio–based potential energy and dipole moment surfaces. The calculated spectra compare well with a low-resolution experimental spectrum except below 1000 cm –1 , where the experimental spectrum shows no absorption. The present calculations find substantial absorption features below 1000 cm –1 , in qualitative agreement with earlier classical calculations of the spectrum. The major spectral bands are analyzed in terms of the molecular motions. Of particular interest is an intense feature at 200 cm –1 , which is due to an isomerization mode that connects two equivalent minima. Very recent high-resolution jet-cooled spectra in the CH stretch region (2825 to 3050 cm –1 ) are also reported, and assignments of the band origins are made, based on the present quantum calculations.
- Published
- 2006
49. Ab Initio Potential Energy and Dipole Moment Surfaces of (H2O)2
- Author
-
Bastiaan J. Braams, Xinchuan Huang, and Joel M. Bowman
- Subjects
Dipole ,Water dimer ,Chemistry ,Moment (physics) ,Potential energy surface ,Ab initio ,Counterpoise ,Physical and Theoretical Chemistry ,Atomic physics ,Potential energy ,Basis set - Abstract
A full-dimensional ab initio potential energy surface (PES) and dipole moment surface (DMS) are reported for the water dimer, (H2O)2. The CCSD(T)-PES is a very precise fit to 19,805 ab initio energies obtained with the coupled-cluster (CCSD(T)) method, using an aug-cc-pVTZ basis. The standard counterpoise correction was applied to approximately eliminate basis set superposition errors. The fit is based on an approach that incorporates the permutational symmetry of identical atoms [Huang, X.; Braams, B.; Bowman, J. M. J. Chem.Phys. 2005, 122, 044308]. The DMS is a fit to the dipole moment obtained with Møller-Plesset (MP2) theory, using an aug-cc-pVTZ basis. The PES has an RMS fitting error of 31 cm(-1) for energies below 20,000 cm(-1), relative to the global minimum. This surface can describe various internal floppy motions, including various monomer inversions, and isomerization pathways. Ten characteristic stationary points have been located on the surface, four of which are transition structures and the rest are higher order saddle points. Their geometrical and vibrational properties are presented and compared with available previous theoretical work. The CCSD(T)-PES and MP2-DMS dissociate correctly (and symmetrically) to two H2O monomers, with D(e) = 1665.7 cm(-1) (19.93 kJ/mol). Accurate quantum calculations of the zero-point energy of the dimer (using diffusion Monte Carlo) and the monomers (using a vibrational configuration interaction approach) are reported, and these together with D(e) give a value of D0 of 1042 cm(-1) (12.44 kJ/mol). A best estimated value is 1130 cm(-1) (13.5 kJ/mol).
- Published
- 2005
50. Ab Initio Diffusion Monte Carlo Calculations of the Quantum Behavior of CH5+ in Full Dimensionality
- Author
-
Bastiaan J. Braams, Joel M. Bowman, T. Alex Brown, Zhong Jin, Anne B. McCoy, and Xinchuan Huang
- Subjects
Surface (mathematics) ,Chemistry ,Potential energy surface ,Ab initio ,Diffusion Monte Carlo ,Physical and Theoretical Chemistry ,Atomic physics ,Quantum ,Curse of dimensionality - Abstract
We report an ab initio calculation of the potential surface, quantum structures, and zero-point energies of CH5+ and CH2D3+ in full dimensionality. This potential energy surface is a very precise f...
- Published
- 2004
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