Search

The pump-probe technique for investigating vibrationally excited states via high resolution Raman spectroscopy was applied to CH methane isotopologue. The dipole transitions between A totally symmetric vibrational states are not active in IR spectra but these states can be efficiently studied using selective high resolution Raman spectroscopy. 80 vibration-rotation transitions, most of which belong to the 2ν– ν band have been assigned in the observed Raman spectra reported in this work. Including the Raman transitions in the simultaneous data fit improves the accuracy of the effective Hamiltonian and also rovibrational upper state levels of the ν, 2ν and 2ν (A) bands. A more accurate model of the ν vibration-rotation transitions improves the interpretation of the temperature dependence of Raman spectra involving the Pentad and Tetradecad polyads., Part of the research was performed at Institute of Monitoring of Climatic and Ecological Systems under contract of Russian Science Foundation (RSF), grant No. 19-77-10046. The research at the V.E. Zuev Institute of Atmospheric Optics was supported by the Ministry of Science and Higher Education of the Russian Federation (V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Sciences). The supports of the CNRS (France) in the frame of “Laboratoire International Associé SAMIA”, of IDRIS / CINES computer centers of France and of the ROMEO computer center Reims-Champagne-Ardenne are acknowledged. R.Z. Martínez, D. Paredes-Roibás and D. Bermejo acknowledge the funding received from Project FIS2017-84391-C2-1-P of Ministerio de Economía y Competitividad.

International audience; This work presents a comparison between experimental and calculated values for the collisional line broadenings and shifts of the S-0(0), S-0(1), and S-0(2) lines of the rotational Raman spectrum of D-2 perturbed by He at 77, 195, and 300K. The pure rotational Raman spectra were obtained by means of a stimulated Raman spectroscopy experimental setup. Close coupling dynamical calculations were performed on the most recent ab initio H-2-He potential energy surface. The resulting scattering matrix elements implemented in the general Hess method allow us to provide pressure broadening, pressure shifting, and Dicke coefficients from 10 to 400K. Experimental and calculated values agree well with each other.

Ministry of Economy and Competitiveness. Grant Number: FIS2012-38175 Universita di Bologna Ministero dell'Istruzione dell'Universita e della Ricerca

High-resolution stimulated Raman spectra of13C2H4 in the regions of the ν2 and ν3 Raman active modes have been recorded at two temperatures (145 and 296 K) based on the quasi continuous-wave (cw) stimulated Raman spectrometer at Instituto de Estructura de la Materia IEM-CSIC in Madrid. A tensorial formalism adapted to X2Y4 planar asymmetric tops with D2h symmetry (developed in Dijon) and a program suite called D2hTDS (now part of the XTDS/SPVIEW spectroscopic software) were proposed to analyze and calculate the high-resolution spectra. A total of 103 and 51 lines corresponding to ν2 and ν3 Raman active modes have been assigned and fitted in wavenumber with a global root mean square deviation of 0.54 × 10−3 and 0.36 × 10−3 cm−1, respectively. Due to the fact that the Raman scattering effect is weak, we did not perform in this contribution the line intensities analysis. Copyright © 2016 John Wiley & Sons, Ltd.

12 pags., 15 figs., 3 tabs., 2 apps., We report theoretical and experimental line-shape parameters for He-perturbed pure rotational HD lines that are relevant for the studies of gas giants atmospheres. Besides the usual pressure broadening and shift parameters, we also report their speed dependencies and Dicke parameters. The theoretical values, obtained from quantum dynamical calculations, are for the R(j=0-3) lines and S(j=0-2) and temperatures from 10 to 500 K. The measurements, performed using stimulated Raman spectroscopy, were done for the S(j=0-2) rotational Raman lines at 77, 195 and 298 K. We also compare the results of our calculations with pressure broadening and line shift coefficients available in the literature at 77, 195 and 300 K for the studied R lines. We demonstrate that a simple Voigt profile is insufficient to accurately model the shapes of He-perturbed HD lines at conditions relevant to gas giants atmospheres, and one should incorporate also the speed-dependent effects and velocity-changing collisions., RZM and DB acknowledge the funding received from Project FIS2017-84391-C2-1-P of Ministerio de Economía y Competitividad.PW contributionis supported by the National Science Centre in Poland through Projects Nos. 2015/19/D/ST2/02195 and 2018/31/B/ST2/00720. The project is cofinanced by the Polish National Agency forAcademic Exchange under the PHC Polonium program (dec. PPN/X/PS/318/2018). PW and FT are supported by the French-Polish PHC Polonium program (project42769ZKfortheFrenchpart)

3 pags., 1 fig., 2 tabs.-- International Conference on Spectral Lines Shapes 17–22 June 2018, Dublin City University, Ireland, We review our recent experimental and theoretical studies on the spectral line shapes of D2 in helium baths. We also provide the most accurate to date experimental line positions of the first pure rotational Stokes lines, S0(j=0-2), of D2., RZM and DBP acknowledge the funding received from Vicepresidencia de Investigación Cientifica y Técnica of Consejo Superior de Investigaciones Científicas through the Fondo de Apoyo Extraordinario and from Project FIS2017-84391-C2-1-P of Ministerio de Economía y Competitividad. PW contribution is supported by the National Science Centre, Poland, Project no. 2015/19/D/ST2/02195.

HRMS 2017, Helsinki, Finland from the 20th until the 25th of August, 2017. -- http://www.helsinki.fi/kemia/HRMS2017/index.html

3 pags., 1 tab., We present accurate measurements for the wavenumbers of the S(0), S(1), and S(2) pure rotational Raman lines in D. Our measurements improve the accuracy of the previously available experimental data by an order of magnitude. They also show complete agreement with the state-of-the-art ab initio calculations of the D rotational splitting, which include both relativistic and Quantum electrodynamics (QED) corrections., R. Z. M. and D. B. P. acknowledge the funding received from Vicepresidencia de Investigación Cientifica y Técnica of Consejo Superior de Investigaciones Científicas through the Fondo de Apoyo Extraordinario and from Project FIS2017-84391-C2-1-P of Ministerio de Economía y Competitividad. P. W. contribution is supported by the National Science Centre, Poland, Project No. 2015/19/D/ST2/02195.

12 pags.; 5 figs.; 1 tab., © the Owner Societies 2015. We propose new values for the V–V collisional energy transfer rate constant of 14N2 (X1Σg+) at different temperatures in collisions between molecules in the v = 1 and v = 0 vibrational states. The values were obtained experimentally by means of a time-resolved double resonance pump–probe stimulated Raman setup in which the stimulated Raman technique was used for both the pump and the probe stage. The main feature of the experiment is the fact that population pumping is done with rotational (and thus spin) selectivity, that is, only molecules belonging to the ortho spin variety of 14N2 are promoted to v = 1. The probe stage is then used to monitor the decay of this ortho rotational population placed in v = 1 and the emergence of a para population in that same vibrational level. Since the only possible mechanism for the arrival of para population to v = 1 is collisional V–V energy transfer, the evolution of the ortho/para ratio in v = 1 is used to quantify the rate constant of the process. The measurements were conducted at 77, 136, 226 and 300 K. The 300 K value had been measured and calculated before by other authors, but a spread larger than an order of magnitude existed between their results. Our proposed value is more precise than previous ones and lies near the mid-point of that interval. The low-temperature values of the rate constant are reported here for the first time. The availability of data at several temperatures has allowed us to unequivocally determine the existence of a strong negative temperature dependence of the rate constant between 77 and 300 K that exhibits a linear behavior in a Landau–Teller plot in this temperature interval., D.B. and R.Z.M. acknowledge the financial support from the Ministry of Economy and Competitiveness through Research Grant FIS2012-38175.

Poster presented at the High Resolution Molecular Spectroscopy Conference held in Budapest (Hungary) on August 25-30, 2013. More details at the conference web site: http://lmsd.chem.elte.hu/hrms/index.html.

The spectra of the ν1, 2ν1–ν1, ν2, 2ν2, and 3ν2–ν2 bands of CF4 were obtained with a quasi-continuous wave stimulated Raman spectrometer. These five bands were studied at a temperature of 135 and 300 K (for the hot bands). The spectrum of ν1 was obtained at a sample pressure of 2 mbar. For the spectra of the other regions, which are much weaker, higher pressures were used. The analysis has been performed thanks to the xtds and spview softwares developed in Dijon for such highly symmetric molecules. Combining the present results with a previous infrared study, we could determine a very accurate value for the C–F equilibrium bond length, i.e. re = 1.31588(6) A. Copyright © 2013 John Wiley & Sons, Ltd.

R.Z.M. and D.B.P. acknowledge the financial support of the Ministry of Science and Innovation through research grant FIS2009-08069.

International Symposium on Molecular Spectroscopy, 71rd meeting; Champaign-Urbana, Illinois (USA); June 20 - 24, 2016; http://isms.illinois.edu/2016/schedule/2016_Abstract_Book.pdf

DB thanks the Ministerio de Ciencia e Innovacion for financial support of this frame of project FIS2005-02029.

Osmium tetroxide (OsO(4)) is a heavy tetrahedral molecule that constitutes a benchmark for quantum chemistry calculations. Its favorable spin statistics (due to the zero nuclear spin of oxygen atoms) is such that only A(1) and A(2) (T(d) symmetry) rovibrational levels are allowed, leading to a dense but quite easily resolvable spectrum. We reinvestigate here the ν(1)/ν(3) stretching fundamental (940-980 cm(-1)) dyad region and perform new assignments and effective Hamiltonian parameter fits for the main isotopologue ((192)OsO(4)). We also investigate the ν(2)/ν(4) bending fundamental dyad (300-360 cm(-1)) for the first time and perform a preliminary analysis. New experimental data have been obtained at 0.001 cm(-1) resolution using an isotopically pure (192)OsO(4) sample and the Synchrotron SOLEIL light source. Assignments and analyses were performed using SPVIEW and XTDS software, respectively. We provide precise effective Hamiltonian parameters, including the band centers for all of the fundamental levels and rotational constants for the ground state and for all four fundamental levels. We discuss isotopic shifts, estimate the equilibrium rotational constant B(e), and derive a precise value for the equilibrium bond length r(e)(Os-O) = 1.70919(16) Å. We also performed experiments to measure for the first time the IR integrated intensities for the ν(2)/ν(4) bending fundamental dyad. These new data are compared to current ab initio predictions.

D.B.P. and R.Z.M. acknowledge the financial support of the Ministry of Science and Innovation through research grant no. FIS2009-08069.

Rotationally resolved spectrum of 12CH313CH3 in the region of ν5 vibrational fundamental (C C stretch) was observed using stimulated Raman spectroscopy. This spectrum was analyzed with data from the ν12 fundamental and transitions from the ν6, 2ν6–ν6, and 3ν6 torsional bands using a 3-state fit. One torsional component of the ν5 fundamental is perturbed, interacting with its partner in the ν 6 = 4 of the torsional stack of the ground vibrational state. As for normal ethane, the coupling was successfully modeled using a Fermi-type interaction. The results mirror that of 12CH312CH3 in that the inclusion of the Fermi-type interaction reduces the required number of terms in the Fourier expansion of the torsional potential for the ground vibrational state from three (in the 2-state fit) to one, only the term in the barrier height is required.

The high-resolution stimulated Raman spectrum of the 2ν10 band located at 1664.16 cm−1 of C2H4 has been reanalyzed, thanks to the tensorial formalism developed in Dijon for X2Y4 asymmetric-top molecules. A total of 191 lines were assigned and fitted as a single band without including perturbations such as Fermi or Coriolis coupling constants. We obtained a global root mean square deviation of 8.5 × 10−3 cm−1. Further investigations are required to include interactions with the ν2 and ν7 + ν10 bands. Copyright © 2009 John Wiley & Sons, Ltd.

The Raman spectrum of the 13CH12CH molecule in the region of its ν2 vibrational band was recorded at a resolution of 2.6 × 10-3 cm-1 and analyzed. Several Q branches were observed and identified, corresponding to the ν2 fundamental and the associated hot bands ν2 + ν4 - ν4, ν2 + ν5 - ν5, ν2 + 2ν4 - 2ν4 and 2ν2 - ν2. The usual normal modes of vibration in acetylene, with the symmetric (ν1) and antisymmetric (ν3) CH stretchings, the CC stretching (ν2), the degenerate trans (ν4) and cis (ν5) bendings were adopted. All the spectra were obtained using the experimental technique of quasi-continuous stimulated Raman spectroscopy. The fundamental ν2 band and the ν2 + ν4 - ν4 and ν2 + ν5 - ν5 hot bands were recorded at room temperature, while ν2 + 2ν4 - 2ν4 was recorded at a temperature of 355 K. Finally, the spectrum of the 2ν2 - ν2 band was recorded at 170 K using a Raman-Raman double resonance technique in which a stimulated Raman pumping process is used to populate a single rotational level of the v2 = 1 state, prior to the spectroscopy stage. A 15 ns delay between pump and spectroscopy is introduced to allow partial collisional relaxation of the rotational population of v 2 = 1 among rotational levels. The assigned Raman transitions and several previously observed infrared bands have been simultaneously fitted in order to derive a set of deperturbed molecular parameters, including the quartic anharmonic coupling coefficients K1,255 and K3,245. The ro-vibrational pattern of the stretching and stretching-bending combination states and an accurate description of the anharmonic resonances in this molecule have been obtained. Copyright © 2013 John Wiley & Sons, Ltd., R.Z.M. and D.B.P. acknowledge the financial support of the Ministry of Science and Innovation through research grant FIS2009-08069.

10 págs.; 9 figs.; 1 tab., The Hartmann–Tran profile (HTP), which has been recently recommended as a new standard in spectroscopic databases, is used to analyze spectra of several lines of H2O diluted in N2, SF6, and in pure H2O. This profile accounts for various mechanisms affecting the line-shape and can be easily computed in terms of combinations of the complex Voigt profile. A multi-spectrum fitting procedure is implemented to simultaneously analyze spectra of H2O transitions acquired at different pressures. Multi-spectrum fitting of the HTP to a theoretical model confirms that this profile provides an accurate description of H2O line-shapes in terms of residuals and accuracy of fitted parameters. This profile and its limiting cases are also fit to measured spectra for three H2O lines in different vibrational bands. The results show that it is possible to obtain accurate HTP line-shape parameters when measured spectra have a sufficiently high signal-to-noise ratio and span a broad range of collisional-to-Doppler line widths. Systematic errors in the line area and differences in retrieved line-shape parameters caused by the overly simplistic line-shape models are quantified. Also limitations of the quadratic speed-dependence model used in the HTP are demonstrated in the case of an SF6 broadened H2O line, which leads to a strongly asymmetric line-shape. & 2015 Elsevier Ltd. All rights reserved., The research is part of the program of the National Laboratory FAMO in Toruń, Poland, and is supported by the Polish National Science Centre Projects nos. DEC-2011/01/B/ST2/00491 and DEC-2013/11/D/ST2/ 02663. The research is also supported by the Foundation for Polish Science TEAM Project co-financed by the EU European Regional Development Fund. A. Cygan is partially supported by the Foundation for Polish Science START Project. Dr. Hodges is supported by the Greenhouse Gas and Climate Sciences Measurement Program of the National Institute of Standards and Technology. Drs. Bermejo and Domenech have been supported by Grants CSD2009-00038 (Consolider Astromol) and FIS2012- 38175 from the Spanish Ministry of Economy and Competitiveness.

Stimulated Raman spectroscopy has been used to study rotationally resolved Q-branch of the ν3 band. This spectrum is analyzed with data from the ν9 fundamental, ν9 + ν4 - ν4 hot band and transitions from ν4 and 3ν4 torsional bands. One torsional component of the ν3 fundamental is near degenerate with its interacting partner v4 = 5 of the ground state torsional bath. The coupling was modeled using a Fermi-type interaction. The introduction of the Fermi-type interaction causes a large change in the barrier height for the ground vibrational state and makes the barrier shape parameter redundant, indicating the vibrational contributions to the experimental barrier shape are dominant. © 2006 Elsevier B.V. All rights reserved., Spanish DGI of the Ministry of Education and Science for financial support through project FIS2005 0209.

The paper reports on a detailed study of the N2–H2 collisional line broadening coefficient. High resolution stimulated Raman spectra of nitrogen–hydrogen mixtures have been recorded at liquid nitrogen and room temperatures. Corresponding linewidth calculations have been performed at temperatures between 77 and 500 K using the semiclassical Robert and Bonamy model for J rotational quantum numbers varying between 0 and 11. Comparison between experimental data and calculated results shows good agreement at room temperature using an adjusted value for the kinetic diameter.

The Raman spectrum of 12C2H4 has been recorded in the 1343–1347cm−1, 1617–1626cm−1 and 1651–1664cm−1 regions using an inverse Raman technique with an instrumental resolution of about 3×10−3cm−1. The Q branches of V3 (CH2 bending, Ag) at 1343.31 cm−1, V2 (CC stretching, A g ) at 1626.17 cm−1 and 2v10 (overtone of CH bending in plane, A g ) at 1664.16 cm−1, were observed and analysed. The recorded bands are of type A, and the selection rules for the transitions are ΔJ=0, ΔK a =0 and ΔK C =0 since only Q branches are strong enough to be observed. The v 2 and 2v10 bands are perturbed owing to a Fermi interaction between the V 2 =1 and v10=2 states, the latter being in turn perturbed by the v 7 =v 10=1 state, at about 1780 cm−1, through a z(a)-type Coriolis interaction. The V3 band has been analysed taking into account the y(c)-type Coriolis interaction between the v3=1 and V 6 =1 levels. Although the v6 fundamental and v 7 +v 10 combination bands have not been detected, their origins and rotational c...

Using a high resolution Raman spectrometer, we have measured Ar-broadening coefficients in the v2 Q branch of C2H2 for 22 lines at 295 K, 20 lines at 174 K, and 16 lines at 134 K. These lines with J values ranging from 1 to 23 are located in the spectral range 1970.9-1974.3 cm-1. The collisional widths are obtained by fitting each spectral line with a Rautian profile. The resulting broadening coefficients are compared with theoretical values arising from close coupling and coupled states calculations. A satisfactory agreement is obtained at room as well as at low temperatures, especially for odd J lines. By comparing broadening coefficients at 295, 174, and 134 K from a simple power law, the temperature dependence of these broadenings has been determined both experimentally, and theoretically. © 2004 Elsevier Inc. All rights reserved., Spanish DGI, project No. REN2002-01618.

The infrared and Raman spectra of deuterated acetylene containing one 13C atom, 13C12CD2, have been recorded and analysed to obtain detailed information on the fundamental 2 band and associated combination and hot bands. Infrared spectra were recorded at 0.004 cm1 resolution in the region 11502900 cm1, which contains combination and hot bands associated with the ground and the bending v4 = 1 and v5 = 1 states. The Qbranches of the 2 fundamental and associated hot bands (2+44, 2+55, 2+2424, 2+2525 and 2+4+5 (4+5)) were recorded using inverse Raman spectroscopy, with an instrumental resolution of about 3103 cm1. In addition, the observation of the 222 Raman band was carried out by populating the v2 = 1 state by stimulated Raman pumping. In total, 11 Raman and 9 infrared bands were analysed, involving all the lvibrational components of the excited stretchingbending states up to vt = v4 + v5 = 2. A simultaneous analysis of all infrared and Raman assigned transitions has been performed on the basis of a theoretical model which takes into account the rotation and vibration ltype resonances within each vibrational manifold and the DarlingDennison anharmonic resonance between the 2+24 and 2+25 states. The obtained parameters reproduce the assigned wavenumbers with a standard deviation of the same order of magnitude as the experimental uncertainty

The Raman spectra of the Q branches of the hot bands associated with the ν2 stretching fundamental of 13 C 2 D 2 (ν 2 +ν 4 –ν 4 , ν 2 +ν 5 –ν 5 , ν 2 +2ν 4 –2ν 4 , ν 2 +2ν 5 –2ν 5 , ν 2 +ν 4 +ν 5 –(ν 4 +ν 5 )) have been recorded using inverse Raman spectroscopy with an instrumental resolution of about 3×10 −3 cm −1 . A simultaneous analysis of all the assigned transitions has been performed on the basis of a theoretical model which takes into account the rotational and vibrational l-type resonances within each vibrational manifold and the Darling–Dennison anharmonic resonance between the ν2+2ν4 and ν2+2ν5 states. The determined parameters reproduce the assigned wavenumbers with a standard deviation of the same order of magnitude as the experimental uncertainty.

The four fundamental bands of 70 GeD 4 have been analyzed using the STDS software developed in Dijon (http://www.u-bourgogne.fr/LPUB/sTDS.html). Both infrared and Raman spectra were used to observe all fundamental bands. Infrared spectra of monoisotopic 70 GeD 4 were recorded in the regions 600 and 1500 cm −1 using the Bruker 120HR interferometer at Wuppertal. The resolution (1/maximum optical path difference) was between 2.3 and 3.3×10 −3 cm −1 for the ν 3 and ν 4 infrared-active fundamental bands as well as for the interacting ν 2 band. A high-resolution stimulated Raman spectrum of the ν 1 band has been recorded in Madrid. The instrumental resolution of the Raman spectrum was 3.3×10 −3 cm −1 . We have performed a global fit of the ground state, ν 2 /ν 4 bending dyad, and ν 1 /ν 3 stretching dyad. We have used 1146, 139, and 676 assigned lines for ν 2 /ν 4 , ν 1 , and ν 3 , respectively. The standard deviation is 2.2×10 −3 cm −1 for the bending dyad, 1.6×10 −3 cm −1 for the ν 3 infrared lines, and 1.7×10 −3 cm −1 for the ν 1 Raman lines. These results enabled us to perform the first experimental determination of the equilibrium bond length of germane as r e =1.5173(1) A.

The stretching fundamental bands of the isotopically substituted acetylene 13C2D2 have been recorded and analysed. The Raman spectra of the Q branch of v 1 and v 2, Σ+ g -Σ+ g bands, have been recorded with an instrumental resolution of about 3.0 x 10−3 cm−1 using inverse Raman spectroscopy. The infrared spectrum has been recorded in the region between 2350 cm−1 and 2500 cm−1 with an instrumental resolution of 4.0 x 10−3 cm−1. Transitions belonging to the v 3, Σ+ u -Σ+ g , fundamental band have been identified and assigned. The vibrational energies and the rotational and centrifugal distortion constants of the excited states of all the observed transitions have been determined. The molecular parameters obtained reproduce the assigned wave-numbers with a standard deviation of the same order of magnitude as the experimental uncertainty.

We present measurements of Raman linewidths in the fundamental Q branch of CO for mixtures with Ar at temperatures of 77, 195, and 300 K, recorded using an inverse Raman spectrometer. Starting from a recent ab initio potential energy surface, theoretical values of Ar broadening coefficients for CO infrared and Raman lines (isotropic and anisotropic components) at temperatures in the range 77 to 1100 K are calculated via quantum-mechanical methods. The relative merits of the close coupling theoretical results over the coupled states results are underlined. Finally, a comparison of the calculated pressure broadening coefficients is made with the present experimental data as well as with recently available infrared data. There is general agreement between the calculated and measured values of the broadenings for all the temperatures probed. We conclude that the temperature dependence of the infrared and Raman broadening coefficients have been correctly determined theoretically and may be used to test a commo...

The high-resolution Raman spectrum of the Q , R , and S branches of the ν 5 bending fundamental of SF 6 has been recorded at a temperature of 195 K (dry ice) and a pressure of 39 mbar. This is the first study ever performed of a ν 5 band of an XY 6 molecule. It has been analyzed thanks to the HTDS software ( http://www.u-bourgogne.fr/LPUB/shTDS.html ) developed in Dijon. This contribution should be of help in understanding the role hot bands in the strong absorbing ν 3 region.

A high-resolution rovibrational Raman spectrum of a sample of Cl 2 has been recorded at room temperature using a quasi-cw stimulated Raman technique. Three Q -branch structures belonging to the fundamental vibrations of the three chlorine isotopomers present in the sample in natural abundances and two weaker Q branches belonging to the first hot bands of the two more abundant isotopomers, 35 Cl 2 and 35 Cl 37 Cl, have been observed. Lines with values of J up to 60 for the fundamentals and 50 for the hot bands have been measured in these fully resolved structures. Some additional lines belonging to O and S branches of the fundamentals and hot bands have also been recorded. The analysis of these data has rendered a new and more precise set of rotational molecular constants and band origins for the first three vibrational states of the chlorine isotopomers.

We present experimental nitrogen-broadening coefficients derived from Voigt profiles of isotropic Raman Q-lines measured in the ν2 band of acetylene (C2H2) at 150K and 298K, and compare them to theoretical values obtained through calculations that were carried out specifically for this work. Namely, full classical calculations based on Gordon[U+05F3]s approach, two kinds of semi-classical calculations based on Robert-Bonamy method as well as full quantum dynamical calculations were performed. All the computations employed exactly the same ab initio potential energy surface for the C2H2-N2 system which is, to our knowledge, the most realistic, accurate and up-to-date one. The resulting calculated collisional half-widths are in good agreement with the experimental ones only for the full classical and quantum dynamical methods. In addition, we have performed similar calculations for IR absorption lines and compared the results to bibliographic values. Results obtained with the full classical method are again in good agreement with the available room temperature experimental data. The quantum dynamical close-coupling calculations are too time consuming to provide a complete set of values and therefore have been performed only for the R(0) line of C2H2. The broadening coefficient obtained for this line at 173K and 297K also compares quite well with the available experimental data. The traditional Robert-Bonamy semi-classical formalism, however, strongly overestimates the values of half-width for both Q- and R-lines. The refined semi-classical Robert-Bonamy method, first proposed for the calculations of pressure broadening coefficients of isotropic Raman lines, is also used for IR lines. By using this improved model that takes into account effects from line coupling, the calculated semi-classical widths are significantly reduced and closer to the measured ones. © 2014 Elsevier Ltd., D.B. and R.Z.M. acknowledge the financial support of the Ministry of Economy and Competitiveness through Research Grant FIS2012-38175. Q.M. acknowledges the financial support from NSF under Grant 1228861. D.B., R.Z.M and F.T. acknowledge financial support from the European GDRI HiRESMIR (high resolution microwave, infrared and Raman molecular spectroscopy).

The fundamental isotropic Raman Q-branch of CO has been recorded using Raman loss spectroscopy for mixtures with helium at low temperatures (77–195 K). Accurate close coupling calculations of both diagonal and off diagonal (line coupling) cross sections have been performed starting from one of the best available potential energy surfaces [T. G. A. Heijmen, R. Moszynski, P. E. S. Wormer, and Ad van der Avoird, J. Chem. Phys. 107, 9921 (1997)]. Predictions are in good agreement with Q-branch Raman data. These results, which corroborate previous analysis based on IR absorption data, are a further test of the adequacy of the close coupling formalism for the prediction of line shapes in a rather wide range of physical situations (pressure, temperature, type of spectroscopy…), when an accurate potential exists.

The Raman spectra of the Q branch of the ν2 band of 12C2D2 and associated hot bands (ν2+ν4−ν4, ν2+ν5−ν5, ν2+2ν4−2ν4, ν2+2ν5−2ν5, ν2+ν4+ν5−(ν4+ν5), and 2ν2−ν2) have been recorded with an instrumental resolution of about 3×10−3 cm−1 and analyzed. All of them have been recorded using high resolution inverse Raman spectroscopy. For 2ν2−ν2, this technique has been combined with stimulated Raman pumping in order to populate the υ2=1 state. A simultaneous analysis of all the observed Raman transitions and of the ν2−ν5 band recorded in the infrared region has been performed on the basis of a theoretical model which takes into account the rotational and vibrational l -type resonances within each vibrational manifold and the Darling–Dennison anharmonic resonance between the ν2+2ν4 and ν2+2ν5 states. The determined parameters reproduce the assigned wavenumbers with a standard deviation of the same order of magnitude as the experimental uncertainty.

High-resolution Raman spectra of the nu(2) band of SF(6) have been recorded at a temperature of 195 K (dry ice) and a pressure of 39 mbar. These spectra were analyzed using a new set of programs specially written for XY(6) molecules. These programs, called HTDS (highly spherical top data system) in reference to the set of programs called STDS (spherical top data system written for XY(4) molecules) can be freely accessible through ftp (user anonymous) at jupiter.u-bourgogne.fr or on the web at the URL http://www.u-bourgogne.fr/LPUB/shTDS.html. The study of nu(2) was made using a Hamiltonian developed through the third order. Four parameters were determined. The standard deviation obtained using about 559 data up to J61 is 0.0021 cm(-1). This result is used to refine by simultaneous analysis the nu(2) and nu(2) + nu(6) bands of SF(6). This new fit allows the determination for the first time of some nu(6) parameters. The values obtained for this band (forbidden in Raman and in infrared) will be used to study the infrared hot bands in the nu(3) and nu(4) regions. Copyright 2000 Academic Press.

In this study we report the first measurements of the pressure-induced lineshift coefficients due to Ar, He, O(2), and N(2) for 22 rovibrational lines from P(53) to R(53), belonging to the 2nu(3) band of (16)O(12)C(32)S at 4100 cm(-1). The lineshift results were obtained from the simultaneous record of the pressure-broadened and pure low-pressure OCS lines, using a tunable difference-frequency laser spectrometer. For four lines of the 2nu(3) band we also report Ar-, He-, O(2)-, and N(2)-broadening coefficients by fitting Voigt and Rautian profiles to the measured shapes of these lines. The broadening and shift coefficients are compared to the results of theoretical calculations based on the semiclassical Robert-Bonamy formalism and two different isotropic and anisotropic intermolecular potentials. For OCS-Ar we also consider the Smith-Giraud-Cooper model including all orders of the interaction within the peaking approximation. In all cases, the calculated broadening coefficients are in reasonable agreement with the experimental data. By considering adjustable parameters for the vibrational dependence of the isotropic potential, the general trends of the lineshifts with J can be roughly predicted, except at low J values where an asymmetry behavior for P and R branches is generally observed. Copyright 2000 Academic Press.

The Raman spectra of the Q branches of the ν1+ν2−ν2 band of 12C2H2 and of the ν1+ν2−ν2 and 2ν2+2ν5−ν2 bands of 13C2H2 were recorded at high resolution in the gaseous phase. To obtain the spectra a two-step pump/probe technique was used. In the first step, molecules were pumped from the ground to the v2=1 excited state by means of a double pulsed stimulated Raman process. Then, spectra corresponding to the transitions from this state to higher ones are recorded by means of a high resolution quasicontinuous stimulated Raman process. The analysis of the experimental data, taking into account the fourth-order anharmonic interaction coupling the excited states for the 13C isotopomer, provided unperturbed values for the rotational and distortion constants of the excited states and for the band origins. Accurate values for the x120 anharmonicity constant have been calculated directly from the energies of the v1=v2=1 states for the first time.

The high-resolution Raman spectra of the ν 4 bands of 11 B 2 H 6 and 11 B 10 BH 6 have been recorded and analyzed. The recordings have been made using a high-resolution spectrometer based on the inverse Raman effect. Q branches have been observed, but P and R branches were too weak to be seen, and simulations of the observed band contour have been necessary to complete the analysis. A weak Coriolis resonance with the 2ν 10 level is present in the 11 B 2 H 6 spectrum. The band centers obtained are 790.9829(12) and 804.76985(27) cm −1 for 11 B 2 H 6 and 10 B 11 BH 6 , respectively (uncertainties are type A with a coverage factor k = 1, i.e., 1 standard deviation).

High-resolution tunable laser measurements of rovibrational line shapes in Arbroadened HF [A.S. Pine, J. Chem. Phys., 1994, 101, 3444] have shown the need of partially correlated Dicke narrowing models to accurately describe the observed asymmetries. A strong collision model accounting for both velocity-and state-changing mechanisms (VCD) and phase-changing ones (D), is presented. The resulting line shape justifies, on a physical basis, the empirical model previously used to interpret the observed features. The present partially correlated strong collisional model leads to a clearer interpretation of the characteristic parameters determined from the experiment for HF-Ar. Further theoretical calculations and experiments show that the residual discrepancies for the first rovibrational lines cannot be attributed to the speed dependence of the collisional line shape parameters. © 1999 Elsevier Science Ltd. All rights reserved.

A generalization of a previously reported technique for investigating vibrationally excited states via high resolution Raman spectroscopy is proposed. In a first step, a vibrational state, typically not accessible by a dipole moment transition from the ground state, is populated in a pulsed stimulated Raman process. After a delay of several nanoseconds, a high resolution spectrum corresponding to transitions from this long lived state is recorded following a quasi-cw stimulated Raman spectroscopy scheme. The use of a pulsed dye laser for providing one of the pumping radiations overcomes some of the limitations of the previously proposed scheme, where this radiation was generated by a Raman shifter filled at relatively high pressure with the gas under study. Experimental aspects are discussed and the spectra of the Q branches of 2ν2(Σg+)–ν2(Σg+) of 12C2H2 and 13C2H2 are presented. The analysis of the measured transitions yielded accurate values of the spectroscopic parameters for the v2=2 vibrationally exc...

The strengths of 100 lines in the 2nu3 band of 16O12C32S have been measured at high resolution in the spectral range 4069-4118 cm-1, using a tunable difference-frequency laser spectrometer. These intensities were obtained by fitting Voigt profiles to the measured shapes of the lines. The vibrational transition moment [(2.141plusmn; 0.020) x 10(-2) D] and the absolute intensity (16.19plusmn; 0.24 cm-2 atm-1 at 296 K) of the 2nu3 band of 16O12C32S are determined from these linestrength measurements. Copyright 1997 Academic Press. Copyright 1997Academic Press

13 p. : gráf., Fully quantal scattering calculations are carried out for CO in argon using both the close coupling~CC! and coupled states ~CS! methods. CC and CS cross sections s( j!j8) generally agree to within 15% or less with the exception of those corresponding to low Dj5u j82ju values at low j where differences may reach 50%. The discrepancy arises mostly from efficient collisions with large orbital angular momentum, where the rotation of the quantization axis can no longer be neglected. Then, the CC calculations were used to test a scaling procedure based on the energy corrected sudden ~ECS! approximation: given a set of basic cross-section s( j!0), is it possible to predict the entire so( j!j8) relaxation matrix? The ECS procedure yields reasonable agreement, on average,at the 13% level. However it fails at reproducing the Dj51 cross sections in cases where the concept of a mean adiabaticity factor losses its physical meaning since the duration of the efficient collisions varies too much with the orbital angular momentum. On that basis, we have examined another question: the validity of an inversion procedure, based on the ECS scheme. Is it possible to determine the basic cross sections s( j!0) starting from the knowledge of the easily measurable diagonal elements so( j!j)? The ECS inverted basic rates agree with the CC ones to within about 20% up to j515 and strongly diverge for higher j while the inversion leads to an overestimation of the mean duration of the efficient collisions. Then, using a high resolution Raman spectrometer, we recorded the Q-branch head of the fundamental band of CO in mixture with Ar at three temperatures, 87, 195, and 300 K, and total pressures up to 1.25 bar. Line-mixing effects in experimental Raman profiles are compared with CC theoretical predictions. Finally the close coupling results are also used to predict rotational relaxation times measured in free jets. © 2003 American Institute of Physics., Financial support from Spanish DGI under Project No. REN2002-01618

We present high-resolution stimulated Raman spectra of the first hot band of nitrogen, 14N2, obtained under conditions of low sample pressure and temperature. The use of a Raman optical pumping system allowed us to transfer a significant amount of population to the v = 1 vibrational state, which made possible the observation of the aforementioned hot band with good S/N ratio without resorting to the use of high temperatures or pressures. This has resulted in a more precise and accurate determination of the peak positions than previously existing ones, which in turn has yielded improved values for the molecular constants obtained from the analysis. The rotational selectivity of the pumping process (only one rotational state is initially populated in v = 1), coupled with the negligible probability of nuclear spin interconversion in the time frame of the experiment, has allowed us to observe the hot band spectra of the ortho and para species of 14N2 separately. Copyright © 2013 John Wiley & Sons, Ltd., The authors acknowledge the funding received from the Spanish Ministry of Science and Innovation through Research Grant FIS2009-08069.

The pressure-induced shifting coefficients for self-, He-, Kr-, O 2 -, and N 2 -broadened lines of CO in the first overtone band have been measured using a tunable difference-frequency laser spectrometer. The lineshift was directly obtained from the simultaneous record of the pressure-broadened line and the same line of pure CO at low pressure. Comparisons are made with results of theoretical calculations based on a semiclassical model and different interaction potentials. It is shown that the lineshifts mainly originate from vibrational dephasing effects. Although the finer details of the J dependence of the shifts are not accurately reproduced, their general trends are well predicted through the calculations.

The characteristics of a commonly used pulsed valve for the production of free jets and molecular beams are analyzed in detail. Special attention is paid to the formation of gas pulses providing a quasisteady flow during a certain time interval within the pulse duration, and to the estimation of a scaling parameter (effective diameter) for the description of the flow field. The adequacy of this effective diameter is checked by performing time-of-flight measurements on molecular beams of Ne, N2, and CH4, and stimulated Raman spectra on free jets of N2 and CH4. © 1995 American Institute of Physics., Financed by the DGI-CYT of Spain under Grants No. PB91-0128 and No. PB92-02194.203.

The modeling of the shape of H 2O lines perturbed by N 2 (and air) using the Keilson-Storer (KS) kernel for collision-induced velocity changes is revisited with classical molecular dynamics simulations (CMDS). The latter have been performed for a large number of molecules starting from intermolecular-potential surfaces. Contrary to the assumption made in a previous study [H. Tran, D. Bermejo, J.-L. Domenech, P. Joubert, R. R. Gamache, and J.-M. Hartmann, J. Quant. Spectrosc. Radiat. Transf. 108, 126 (2007)]10.1016/j.jqsrt.2007.03.009, the results of these CMDS show that the velocity-orientation and -modulus changes statistically occur at the same time scale. This validates the use of a single memory parameter in the Keilson-Storer kernel to describe both the velocity-orientation and -modulus changes. The CMDS results also show that velocity- and rotational state-changing collisions are statistically partially correlated. A partially correlated speed-dependent Keilson-Storer model has thus been used to describe the line-shape. For this, the velocity changes KS kernel parameters have been directly determined from CMDS, while the speed-dependent broadening and shifting coefficients have been calculated with a semi-classical approach. Comparisons between calculated spectra and measurements of several lines of H 2O broadened by N 2 (and air) in the ν 3 and 2ν 1 ν 2 ν 3 bands for a wide range of pressure show very satisfactory agreement. The evolution of non-Voigt effects from Doppler to collisional regimes is also presented and discussed. © 2012 American Institute of Physics., Support of this research by the National Science Foundation (NSF) through Grant No. ATM-0803135; financial support from MICINN through Grant Nos. FIS2009-08069 and Consolider CSD00038.

The high-resolution stimulated Raman spectrum of F2 has been recorded with a quasi cw technique. Q branches of the fundamental and first hot band have been fully resolved. Forty-one transitions of the Q branch of the fundamental up to J = 43 have been measured, in addition to 21 transitions of the O and S branches of this band. Twenty-one transitions of the Q branch of the first hot band up to J = 27 have also been measured. From the analysis of these data a more accurate set of molecular parameters for the v = 0, v = 1, and v = 2 states of this molecule has been derived. From our data and some previous fluorescence data a new set of equilibrium parameters is also proposed.

Infrared and Raman spectra of the ν1 band of ketene, H2CCO, have been recorded at Doppler resolution. The infrared spectrum has been obtained with a difference frequency infrared spectrometer, and the Raman spectrum of the Q branches of this band has been recorded using a stimulated Raman spectrometer. The vib‐rotational analysis of the data is very complicated because of many crossings with other vibrational states, which can interact with v1=1 through Fermi or Coriolis mechanisms. We present a discussion on global and local resonances, and we are able to extract information on the perturbing levels and on the perturbation parameters, even though the perturbing bands are not always detected in the spectrum.

The high-resolution (ca. 0.008 cm −1 ) stimulated Raman spectrum of the strongly perturbed C−H symmetric stretching region of 12 C 2 H 6 at room temperature and at a rotational temperature of ca. 30 K, achieved in a free supersonic jet expansion chamber, is reported. The spectrum is tentatively analysed and assigned in terms of a simplified vibration-torsion-rotation Hamiltonian. Besides the already known strong Fermi resonance, several Coriolis torsional interactions are identified as the major perturbations in this spectral region