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The time constant selected for lock-in amplification (LIA) has a crucial impact on observed line shapes in laser heterodyne spectroscopy, in particular in the case of ground-based remote monitoring of trace gas in the atmospheric column using laser heterodyne radiometer (LHR). Conventional simulation could not allow validation of LHR spectra measured in a real and complex atmospheric environment exhibiting large temporal and spatial variability (humidity, temperature, pressure, etc) that impact significantly the measured LHR spectra profiles. High-precision spectral measurement is thus crucial to avoid any spectral distortion resulting from the measurement. In this paper, the impact of LIA time constant on spectral line shape is investigated for LHR operating in continuous laser tuning mode, based on analysis of laboratory heterodyne spectra, in terms of signal-to-noise ratio (SNR), line width broadening, absorption depth and line shift. With respect to the given frequency scanning speed in continuous mode and to the halfwidth of the absorption feature to scan, a reasonable scanning time ΔTscan, the time needed for scanning laser frequency through the halfwidth ΔνHWHM of the absorption line, equal to or longer than 14 times of the LIA time constant τ is concluded in order to efficiently reduce the noise while without significant shift and distortion of the line shape. Experimental validation was carried out using a laser heterodyne absorption spectroscopy approach in the laboratory. Four different combinations of time constants τ and scanning time ΔTscan were used to record heterodyne spectra of a CH4 absorption line near 1242.00 cm−1 in continuous laser tuning mode. An optimal combination of a scanning time of 137 ms with a time constant of 1 ms was obtained. This optimal combination was used for ground-based measurements of CH4 and N2O in the atmospheric column by LHR. The extracted LHR spectrum is in good agreement with a referenced TCCON (Total Carbon Column Observing Network) FT-IR (Fourier-transform infrared) spectrum. [ABSTRACT FROM AUTHOR]

High resolution spectra of quasar absorption systems provide the best constraints on temporal or spatial changes of fundamental constants in the early Universe. An important systematic that has never before been quantified concerns model non-uniqueness. The absorption structure is generally complicated, comprising many blended lines. This characteristic means any given system can be fitted equally well by many slightly different models, each having a different value of α, the fine structure constant. We use AI Monte Carlo modelling to quantify non-uniqueness. Extensive supercomputer calculations are reported, revealing new systematic effects that guide future analyses: (i) Whilst higher signal to noise and improved spectral resolution produces a smaller statistical uncertainty for α, model non-uniqueness adds a significant additional uncertainty. (ii) Non-uniqueness depends on the line broadening mechanism used. We show that modelling the spectral data using turbulent line broadening results in far greater non-uniqueness, hence this should no longer be done. Instead, for varying α studies, it is important to use the more physically appropriate compound broadening. (iii) We have studied two absorption systems in detail. Generalising thus requires caution. Nevertheless, if non-uniqueness is present in all or most quasar absorption systems, it seems unavoidable that attempts to determine the existence (or non-existence) of spacetime variations of fundamental constants is best approached using a statistical sample. [ABSTRACT FROM AUTHOR]

A new mixed orthophosphate crystal of Nd3+:LuYPO 4 was grown by high temperature solution method successfully. The optical properties including polarized absorption and emission spectra as well as the fluorescence decay curve have been investigated in detail. The calculated absorption cross-sections were 18.6 × 10−20 cm2 at 803 nm with a FWHM of 6.10 nm for π-polarization and 8.96 × 10−20 cm2 at 804 nm with a FWHM of 6.07 nm for σ-polarization, respectively. The broad absorption bands wider than those of Nd:YPO 4 and Nd:LuPO 4 crystals confirm that the incorporation of Lu3+ ions results in a effectively inhomogeneous broadening of the spectra. Based on J-O theory, some typical parameters such as J-O intensity, fluorescence branching rate and radiation lifetime of Nd3+ ions in Nd:LuYPO 4 crystal were systematically calculated. Besides, five strong emission peaks located at 1054, 1061, 1066, 1076 and 1081 nm can be observed obviously from fluorescence spectra. All the results show that Nd:LuYPO 4 crystal is a promising laser material applied to 1.0 μm with multi-wavelength emission characteristics. [Display omitted] • The Nd3+:LuYPO 4 crystal was grown successfully from Pb 2 P 2 O 7 solution. • An effectively inhomogeneous broadening of the spectra at around 808 nm for Nd3+:LuYPO 4 crystal. • Spectral parameters of Nd3+ ions were calculated in detail based on J-O theory. [ABSTRACT FROM AUTHOR]

Highlights • Fourier transform spectroscopy of a mixture of CO with CO 2 in the 2000–2300 cm−1 region. • A spectra analysis was made using Speed dependent Voigt profile. • The CO 2 broadening and shift coefficients for 49 lines of the CO molecule were obtained. Abstract The absorption spectra of a mixture of CO with CO 2 at different partial pressures of CO 2 have been recorded at room temperature in the 2000–2300 cm−1 region using a Bruker IFS 125 HR FTIR spectrometer. To obtain the spectral line parameters for the fundamental band of CO molecule, the quadratic speed-dependent Voigt profile was used for the first time. The CO 2 pressure induced broadening and shift coefficients for 49 spectral lines have been measured. A comparison with the published data is discussed. [ABSTRACT FROM AUTHOR]

An analogy is shown for broadening the spectral line of atoms in the case of competition between the short-range Doppler broadening mechanism and the long-range impact mechanism in atomic gases, as well as for the absorption band of a molecular gas in the infrared (IR) region of the spectrum, where the longrange part of the spectrum is also determined by the impact mechanism of the broadening. The long-range part in the pedestal region of the absorption band is associated with the distribution of molecules over the rotational states, and, in the range of wings of the absorption band, it is due to a finite time of collisions between emitting and perturbed molecules. The flux of resonant radiation produced by an excited atomic gas is estimated using the concepts of the spectral absorption band and a large optical thickness of the gas. These concepts are used for a molecular gas where, in the framework of the regular model (the Elsasser model), expressions are given for the absorption coefficient related to a specific spectral absorption band, separately in the pedestal region and for wings of the absorption band. As a demonstration of the possibilities of these concepts, the IR flux is calculated on the surface of Venus from its atmosphere, which includes seven vibrational transitions of the carbon dioxide molecule and amounts to 26% of the total flux of IR radiation emitted by the Venus surface. An analysis of the Venus energy balance leads to the conclusion that the main part of IR radiation of the Venus atmosphere falling on its surface is formed by a microscopic dust in the Venus atmosphere. This channel of the Venus energy balance is realized if the mass of a microscopic dust in the Venus atmosphere is seven orders of magnitude less than the mass of atmospheric carbon dioxide. [ABSTRACT FROM AUTHOR]

The room temperature absorption spectrum of water vapor highly enriched in 17 O has been recorded by Cavity Ring Down Spectroscopy (CRDS) between 7443 and 7921 cm −1 . Three series of recordings were performed with pressure values around 0.1, 1 and 10 Torr. The frequency calibration of the present spectra benefited of the combination of the CRDS spectrometer to a self-referenced frequency comb. The resulting CRD spectrometer combines excellent frequency accuracy over a broad spectral region with a high sensitivity (Noise Equivalent Absorption, α min ∼ 10 –11 –10 −10 cm −1 ). The investigated spectral region corresponds to the high energy range of the first hexade. The assignments were performed using known experimental energy levels as well as calculated line lists based on the results of Partridge and Schwenke. Overall about 4150 lines were measured and assigned to 4670 transitions of six water isotopologues (H 2 16 O, H 2 17 O, H 2 18 O, HD 16 O, HD 17 O and HD 18 O). Their intensities span six orders of magnitude from 10 –28 to 10 –22 cm/molecule. Most of the new results concern the H 2 17 O and HD 17 O isotopologues for which about 1600 and 400 transitions were assigned leading to the determination of 329 and 207 new energy levels, respectively. For comparison only about 300 and four transitions of H 2 17 O and HD 17 O were previously known in the region, respectively. By comparison to highly accurate H 2 16 O line positions available in the literature, the average accuracy on our line centers is checked to be on the order of 3 MHz (10 −4 cm −1 ) or better for not weak well isolated lines. This small uncertainty represents a significant improvement of the line center determination of many H 2 16 O lines included in the experimental list provided as Supplementary Material . [ABSTRACT FROM AUTHOR]

We propose a strategy to generate parameters of the Hartmann-Tran profile (HTp) by simultaneously using first principle calculations and broadening coefficients deduced from Voigt/Lorentz fits of experimental spectra. We start from reference absorptions simulated, at pressures between 10 and 950 Torr, using the HTp with parameters recently obtained from high quality experiments for the P(1) and P(17) lines of the 3-0 band of CO in He, Ar and Kr. Using requantized Classical Molecular Dynamics Simulations (rCMDS), we calculate spectra under the same conditions. We then correct them using a single parameter deduced from Lorentzian fits of both reference and calculated absorptions at a single pressure. The corrected rCMDS spectra are then simultaneously fitted using the HTp, yielding the parameters of this model and associated spectra. Comparisons between the retrieved and input (reference) HTp parameters show a quite satisfactory agreement. Furthermore, differences between the reference spectra and those computed with the HT model fitted to the corrected-rCMDS predictions are much smaller than those obtained with a Voigt line shape. Their full amplitudes are in most cases smaller than 1%, and often below 0.5%, of the peak absorption. This opens the route to completing spectroscopic databases using calculations and the very numerous broadening coefficients available from Voigt fits of laboratory spectra. [ABSTRACT FROM AUTHOR]

A Bruker IFS 125 HR Fourier transform spectrometer was used to measure several pure water transmittance spectra in the spectral range 1850–4000 cm −1 . A total of 15 measurements with absorption path lengths between 24.9 cm and 174.6 m and sample gas pressures from 0.1 to 20 mbar were performed at 296 K. The transmittance spectra were corrected for various error sources and were analyzed in the spectral ranges 1850–2280 cm −1 and 2390–4000 cm −1 for the majority of intensities between 3×10 –26 and 3×10 –19 cm molecule −1 . A multispectrum fitting approach was used applying a quadratic speed-dependent Voigt model extended to account for line mixing in the Rosenkranz first order perturbation approximation. Line positions, intensities, self-broadening widths, their speed-dependence and in some cases line mixing had to be adjusted for fitting the measurements to noise level. An extensive error estimation calculation was performed propagating several instrumental and measurement errors into individual parameter inaccuracies. The determined parameters are compared to HITRAN12 and independent experimental values while intensities are compared to recent ab initio calculations performed at UCL. The overall agreement between ab initio calculations and experimental values is remarkable and below 1% in most cases. The determined line parameters are provided as a supplement to this publication. [ABSTRACT FROM AUTHOR]

Pressure-broadened line shape parameters of transitions in the ν 3 band of HDO (ν 0 = 3707.4 cm -1 ) were measured from spectra of HDO and mixtures of HDO and CO 2 for application to accurate retrievals of HDO abundances and D/H ratios for CO 2 -rich planetary atmospheres of Mars and Venus. A few calculated line lists have recently been published on HDO-CO 2 line shapes and their temperature dependences, but the present study represents the first laboratory measurements of those parameters in the ν 3 band; Measurements for nearly 100 transitions in the ν 3 band have been made. Room temperature measurements of self-broadened width and shift coefficients for all of these transitions, line mixing via off-diagonal relaxation matrix element coefficients and quadratic speed dependence parameter were measured for the majority of these transitions. All these measurements were made by simultaneously fitting eleven high-resolution spectra of HDO and HDO-CO 2 mixtures at various temperatures and pressures recorded with the Bruker Fourier transform spectrometer at the Jet Propulsion Laboratory. Two specially built coolable absorption cells with path lengths of 20.38 cm and 20.941 m were used to contain the sample mixtures. Multispectrum nonlinear least squares fitting algorithm was employed in the analysis. Calculations using the Modified Complex Robert-Bonamy formalism (MCRB) were made for the half-width coefficients, their temperature dependences and pressure shift coefficients for the HDO–CO 2 and HDO–HDO collision systems. The calculations were made for all ν 3 band transitions in the 1100–4100 cm -1 region on the HITRAN2012 database. Present measurements are compared with the MCRB calculations and other literature values. [ABSTRACT FROM AUTHOR]

This paper describes the second part of an extensive study on absorption line parameters of water vapor in the spectral range 1850–4000 cm −1 , dedicated to the use in ground-based atmospheric measurements. Whereas the first part focusses on line positions, intensities and self-broadening line shape parameters, this work deals with air-broadening line shape parameters and temperature dependence. A Bruker IFS 125 HR Fourier transform spectrometer was used to measure air-broadened transmittance spectra of water vapor at 296 K and at low and high temperatures. 24 measurements were performed at 296 K and total pressures from 30 to 1000 mbar and 15 spectra were recorded at temperatures from 213 to 353 K at pressures of 90 or 100 mbar. A multispectrum fitting approach was used for line parameter retrieval applying a quadratic speed-dependent hard collision model extended to account for line mixing in the Rosenkranz approximation. Air-broadened widths, their speed-dependence, air-shift and in some cases collisional narrowing (Dicke-effect) and line mixing had to be fitted for modelling the 296 K measurements to the noise level. Measurements performed at low and high temperatures were used to retrieve temperature dependence parameters for air- and self-broadening, air- and self-shift and in a few cases for line mixing. For every parameter an extensive error estimation calculation was performed propagating several instrumental, measurement and parameter errors into individual parameter inaccuracies. The resulting parameters are presented, discussed and compared to the database HITRAN12. With this work the experimental line list is completed and the parameters are provided as Supplement to this publication. [ABSTRACT FROM AUTHOR]

An infrared laser-absorption technique for in situ temperature and nitric oxide species sensing in high-temperature gases is presented. A pair of quantum cascade lasers in the mid-infrared near 5 μm were utilized to probe rovibrational transitions in nitric oxide's fundamental band. The line parameters of the selected transitions, including line strengths and collision broadening coefficients of nitric oxide with argon and nitrogen, were evaluated during controlled room-temperature static cell experiments and high-temperature shock tube experiments at temperatures between 1000 and 3000 K, and pressures between 1 and 5 atm. These studies provided new insights into the temperature dependence of nitric oxide collision broadening, highlighting the inadequacies of the power law over a broad temperature range. With an accurate spectroscopic model over a broad temperature range, the quantitative two-color temperature sensing strategy was demonstrated in non-reactive shock tube experiments from 1000 to 3000 K to validate thermometry and during a nitric oxide formation experiment near 1700 K and 4 atm to highlight capability for temporally-resolved species measurements at MHz rates. The technique has applicability for sensing in a broad range of flow fields that involve high-temperature air. [ABSTRACT FROM AUTHOR]

Early ERIM measurements of hot-through-cold gas (CO 2 , H 2 O, N 2 ) emission-absorption spectra are replicated by modern line-band computations that incorporate independent fundamental line strength-frequency information. Close agreement is achieved for all cases by empirical adjustment of the line broadening function. Line spectra for CO 2 and H 2 O computed at 0.001 cm −1 resolution were integrated to 3.2 and 14 cm −1 using a triangular slit function consistent with ERIM measurements for the 4.3 and 2.7 μm spectral regions. Band spectra computed at 0.1 cm −1 resolution give close agreement with spectra generated at higher resolution. The findings demonstrate a merged line-band model for nonuniform path radiance and transmittance based on the line-sum spectral cross section for each piecewise-uniform path segment. The band-and-line transmittance become equivalent at high spectral resolution. [ABSTRACT FROM AUTHOR]

This study deals with precise measurements of absolute line intensities, N2-, O2- and Ar- collisional broadening coefficients of N2O in the P-branch of the ν3 vibrational band near 4.5 mm. Collisional broadening coefficients of N2O-air are derived from the N2- and O2- broadening contributions by considering an ideal atmospheric composition. Studies are performed at room temperature for 10 rotational transitions over 2190-2202 cm-1 spectral range using a distributed-feedback quantum cascade laser. To retrieve spectroscopic parameters for each individual transition, measured absorption line shape is simulated within Voigt and Galatry profiles. The obtained results compare well with previous experimental data available in the literature: the discrepancies being less than 4% for most of the probed transitions. The spectroscopic data reported here are very useful for the design of sensors used to monitor the abundance of N2O in earth's atmosphere. [ABSTRACT FROM AUTHOR]

We report measured line intensities and temperature-dependent broadening coefficients of NH 3 with Ar, N 2 , O 2 , CO 2 , H 2 O, and NH 3 for nine sQ( J , K ) transitions in the ν 2 fundamental band in the frequency range 961.5–967.5 cm −1 . This spectral region was chosen due to the strong NH 3 absorption strength and lack of spectral interference from H 2 O and CO 2 for laser-based sensing applications. Spectroscopic parameters were determined by multi-line fitting using Voigt lineshapes of absorption spectra measured with two quantum cascade lasers in thermodynamically-controlled optical cells. The temperature dependence of broadening was measured over a range of temperatures between 300 and 600 K. These measurements aid the development of mid-infrared NH 3 sensors for a broad range of gas mixtures and at elevated temperatures. [ABSTRACT FROM AUTHOR]

Distributions described by the Bloembergen-Rowland (BR) formula and widely used in NMR of solids for studying polycrystalline samples, which is closely connected with the problem of constructing the convolutions of such distributions with a broadening symmetric function, are strictly area normalized. The application of the obtained methodological results is illustrated by the example of the analysis of NMR data for UF. [ABSTRACT FROM AUTHOR]

Room temperature O 2 -broadening coefficients were measured for 16 transitions, from P(23) to R(16), of the ν 4 + ν 5 band of acetylene near 7.5 μm. Absorption spectra of these lines were recorded at room temperature and various pressures, from 20.00 mbar to 66.21 mbar using a tunable diode laser spectrometer. The broadening coefficients were obtained by fitting the Voigt profile as well as the Rautian, the Galatry and the quadratic Speed Dependent Voigt models on the experimental spectra. The results were then compared with some previous studies realized for other bands of acetylene. [ABSTRACT FROM AUTHOR]

The absorption spectra of a mixture of CH4 with CO2 at different partial pressures of both gases have been recorded at room temperature in the 5390-6200cm−1 region using a Bruker IFS 125 HR FTIR spectrometer. The multispectrum fitting procedure has been applied to these spectra to recover the broadening and shift parameters of the methane spectral lines. The CO2 broadening and pressure induced shift coefficients, respectively, for 533 and 386 CH4 spectral lines with good values of the signal to noise ratio have been derived. The rotational dependence of the values of these coefficients is discussed. [ABSTRACT FROM AUTHOR]

• The CO 2 -broadening and shift parameters of about 2000 ethylene lines in the region of the ν 11 absorption band were measured. • A polynomial approximately describing the rotational dependence of the broadening of ethylene by CO 2 pressure is proposed. • The similarity of the CO 2 -broadening coefficient to those of self-broadening was revealed. The absorption spectra of the mixtures of ethylene and carbon dioxide at seven different partial pressures of both gasses have been recorded using the Bruker IFS 125 HR FTIR spectrometer at room temperature in the 3.3 µm region. The multispectrum fitting procedure has been applied to these spectra to recover the spectral line parameters. The broadening and shift coefficients induced in ethylene by carbon dioxide pressure have been obtained for almost 2000 lines in the region of the ν 11 absorption band between 2928 and 3056 cm−1. The rotational dependence of the broadening parameters was analyzed. The similarity of the CO 2 -broadening coefficient to the self-broadening coefficient was revealed and discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

Quantitative agreement between observations and ab initio theory, e.g. to within a few cm−1 for most of the N' = 1–4 excited levels. [Display omitted] • The absorption spectrum of H 2 at room temperature, recorded at high resolution at the BESSY synchrotron radiation storage ring in the 132 500 – 139 000 cm−1 energy range. • More than 1000 absorption transitions assigned to the n pσ 1 Σ u + and n pπ 1 Π u ± series for n ≥ 4 with N' =0 – 4. • Transition frequencies and line intensities quantitatively assigned and results tabulated. • Vibrational progressions followed up to high quantum numbers. • Calculation from first principles of perturbed spectra in H 2 using the Multichannel Quantum Defect Theory approach. Over a thousand spectral lines in the absorption spectrum of molecular hydrogen (H 2) to the n pσ 1 Σ u + and n pπ 1 Π u ± Rydberg levels (n ≥ 4) were measured and assigned for rotational levels with N' =0 – 4 in the spectral range between 132 500 and 139 000 cm−1. The experimental energies, the absorption cross sections, and Einstein A coefficients were compared with ab initio multi-channel quantum defect (MQDT) calculations. The assigned lines include 31P(1), 225 R(0) or P(2), 291 R(1) or P(3), 109 R(2) lines, 71 R(3) lines, and over 300 Q(1–3) lines. Transition energies were determined up to excitation energies of 139 000 cm−1 above the ground state, thereby extending earlier works and leading to several reassignments. The overall agreement between experiment and first principles calculations, without adjustable parameters, is very good in view of the multi-state interferences treated within the MQDT-framework. The line intensities in terms of Einstein A coefficients are well represented in the MQDT-framework. These line intensities follow, in general, the 1/n3 scaling behavior as characteristic in Rydberg series, but many deviations occur which are explained by MQDT. Despite the mostly very good agreement between the observations and the outcome of the MQDT calculations for both level energies and line intensities, some pronounced deviations were found which are discussed. The shortcomings of the MQDT calculations are ascribed to the treatment of the excited states in terms of a 1s n p single electron configuration, therewith neglecting possible interferences with 1s n f or 2s core excited states. So far, some 108 lines remained unassigned. [ABSTRACT FROM AUTHOR]

• Non-Markov perturbation approach to the rotational relaxation matrix. • Formation of satellites in the far wings of allowed IR and Raman lines. • Collision-induced intensity transfer from the peaks of allowed lines to the wings. A non-Markov theory of diffuse satellites developing around the allowed (mother) rotational lines perturbed by monoatomic buffer gases is expounded. As the buffer-gas pressure grows, the lorentzian part of mother lines adjacent to the band origin becomes attenuated because of the intensity transfer to pressure-enhanced satellites. Different channels contributing to the attenuation of infrared and Raman lines of linear molecules are considered. Simple estimations of the attenuation coefficients reasonably fit experimental data available for the HCl and HF absorption spectra perturbed by monatomic gases. [ABSTRACT FROM AUTHOR]

Abstract: The accuracies of the classical and semiclassical methods currently used in collisional spectral line broadening calculations of molecules are compared. The primary goal is to elucidate the validity of each particular method applied to linear molecules that have different rotational constants but which are perturbed by the same atom. Vibration–rotational electric dipole absorption spectra of CO2, C2H2, CO, HCl and HF molecules perturbed by an Ar atom are examined at room temperature. The most accurate vibrationally independent potential energy surfaces (PESs) are applied to all molecular pairs. The following theoretical approaches are involved in cross-examination: two classical schemes (exact C3D and C3Diso) and four semiclassical formalisms (NG—of Neilsen and Gordon, PA—peaking approximation, SGC—of Smith, Giraud and Cooper, and RB—of Robert and Bonamy). Identical “exact” isotropic trajectories, driven by only the isotropic part of the PES, are used in C3Diso and in all semiclassical calculations. The comparison is made with experimental data as well as with benchmark quantum dynamical results obtained in the same conditions within close coupling and coupled states schemes. Quantum results reproduced the experimental data excellently in all cases considered, which is as it should be if the interaction PES is accurate. An exact classical C3D approach displays good results for all molecules. By contrast, NG, PA and SGC semiclassical formalisms seriously underestimate line broadening for molecules with small rotational constants (CO2, C2H2 and, to a lesser extent, CO), mainly due to the use of isotropic trajectories in these schemes. The RB method strongly overestimates line broadening for the majority of values of the rotational quantum number J for all molecules studied. The only exception is the case of HF molecules at high J values, where PA, SGC and RB semiclassical schemes provide good results, coinciding well with quantum CC calculations for J>3. Mean overall magnitudes of relative errors, taking an average over all J values and all five molecules studied and of the methods considered are C3D—11%, C3Diso—14%, NG—14%, PA—12%, SGC—14% and RB—21%. [Copyright &y& Elsevier]

A rapidly swept quantum cascade laser (QCL) has been used to probe a small region of the ν band of formaldehyde around 8 μm by direct absorption spectroscopy. Two of the strongest transitions accessible within the operating region of the QCL are assigned as (1,1,1)←(2,0,2) and (10,1,9)←(9,2,8). In this paper, we report pressure-induced broadening and shift coefficients for these transitions with a variety of gases (He, Ne, Kr, Ar, N, O, and CO). The pressure broadening coefficient measurements are shown (in some cases) to be chirp rate dependent, even under conditions where rapid passage effects are negligible, highlighting the marked difference that can occur between studies with rapidly swept fields and those employing conventional diode laser devices. [ABSTRACT FROM AUTHOR]

Abstract: The Doppler-limited absorption spectrum of the cation was observed using a Ti–Sapphire laser system (in region of 12060–12800cm−1) by optical heterodyne velocity modulation absorption spectroscopy. Precise molecular constants (, , , , ) were obtained for the involved levels by fitting spectral lines of (3, 20) and (4, 21) bands in the Second Negative system using a nonlinear least-squares fitting procedure with the standard Hamiltonians. The vibrational assignment was based on the isotopic effect. More detailed isotopic effects on the molecular constants were discussed as well. [Copyright &y& Elsevier]

Abstract: Photoinduced processes in phthalocyanine-functionalized gold nanoparticles have been investigated by spectroscopic measurements. The zinc phthalocyanine used contained four phenylthio peripheral substituents (ZnPc(SPh)4). The conjugates formed are represented as ZnPc(SPh)4–AuNP. The absorption spectrum of the ZnPc(SPh)4–AuNP shows a broadening of the phthalocyanine Q-band absorption, probably due to a tight packing of the phthalocyanines on the gold nanoparticle surface. For the attached phthalocyanines, the two fluorescence lifetimes obtained by time-correlated single photon counting (TCSPC) were determined to be both longer and shorter than that of the free Pc. The fluorescence lifetimes were resolved using time resolved fluorescence spectroscopy (TRES). [Copyright &y& Elsevier]

Recent experimental observations of time-dependent beatings in the two-dimensional echo-spectra of light-harvesting complexes at ambient temperatures have opened up the question of whether coherence and wave-like behaviour play a significant role in photosynthesis. We carry out a numerical study of the absorption and echo-spectra of the Fenna-Matthews-Olson (FMO) complex in Chlorobium tepidum and analyse the requirements in the theoretical model needed to reproduce beatings in the calculated spectra. The energy transfer in the FMO pigment-protein complex is theoretically described by an exciton Hamiltonian coupled to a phonon bath which accounts for the pigments' electronic and vibrational excitations, respectively. We use the hierarchical equations of motions method to treat the strong couplings in a non-perturbative way. We show that the oscillations in the two-dimensional echo-spectra persist in the presence of thermal noise and static disorder. [ABSTRACT FROM AUTHOR]

Relative coefficients of collisional broadening caused by NO molecules and their temperature dependences are determined for absorption lines (100-001 transition, R-branch) of the CO molecule. [ABSTRACT FROM AUTHOR]

Abstract: Absorption spectra for the transition of the phenyl radical have been recorded using the technique of cavity ring-down spectroscopy. The radicals were produced by an electric discharge through Ar/C6H5Br mixtures and cooled by supersonic expansion. Partially resolved rotational structure was observed for the , , and bands, and excited state rotational constants were derived from these data. For the band, homogeneous line broadening was indicative of an excited state lifetime of 96ps. [Copyright &y& Elsevier]

Abstract: The absorption spectra of methane at different path lengths and different pressures for three temperatures 180, 240 and 296K have been recorded in the 5556–6166cm−1 region using the Bruker IFS 120 HR and 125 HR high-resolution Fourier transform spectrometers. The multispectrum fitting procedure has been applied to these spectra to recover the spectral line parameters. The main goal of this procedure was the determination of self-broadening and self-pressure-induced shift coefficients and the exponents of their temperature dependences. These parameters have been derived for 406 assigned lines with good values of the signal to noise ratio. The rotational dependence of these parameters is discussed. [ABSTRACT FROM AUTHOR]

Abstract: The self-broadening coefficients of acetylene at room temperature have been measured for 10 lines in the P branch of the bands of 12C2H2 and 13C12CH2 near 1.533μm, using a high resolution tunable diode laser spectrometer developed for the Martian space mission PHOBOS-Grunt. The collisional widths are obtained by fitting each recorded line with the Voigt profile as well as the Rautian profile accounting for the collisional Dicke narrowing effect. The standard Voigt model provides slightly smaller broadening coefficients than the Rautian model. Our data are thoroughly compared to the main atmospheric molecule database HITRAN and previous values in various bands of acetylene. Moreover, it is worth noting that a large number of new transitions not listed in the latest HITRAN08 were measured and identified for the first time. [ABSTRACT FROM AUTHOR]

Abstract: We present the results of absorption spectra measurements of ions in the crystal in the vicinity of the transition. We show that satellites accompanying the line of an isolated ion are caused by ion exchange interaction. The structure of these satellite lines, hidden by the inhomogeneous broadening is revealed by means of the double optical resonance technique. Various ion interaction mechanisms which may be responsible for the observed structure are discussed. [Copyright &y& Elsevier]

Abstract: The high resolution absorption spectrum of methane in the 1.58μm transparency window has been recorded at room temperature and at 79K by CW-Cavity Ring Down Spectroscopy using a cryogenic cell and a series of Distributed Feed Back (DFB) diode lasers. The achieved sensitivity (αmin ∼3×10−10 cm−1) has allowed for a detailed characterization of the 6289–6526cm−1 region which corresponds to the lowest opacity of the transparency window. A list of 6868 and 4555 transitions with intensities as weak as 1×10−29 cm/molecule was constructed from the recordings at 297 and 79K, respectively. By comparison with a spectrum of CH3D recorded separately by Fourier Transform Spectroscopy, 1282 and 640 transitions of monodeuterated methane, CH3D, in natural abundance in our sample were identified at 297 and 79K, respectively. The rotational temperature determined from the intensity distribution of the 3ν 2 band of CH3D (79.3K) was found in good agreement with the temperature value previously obtained from the Doppler line broadening. The reduction of the rotational congestion by cooling down to 79K reveals a spectral region near 6300cm−1 where CH3D transitions are dominant. The low energy values of the transitions observed both at 79K and at room temperature were derived from the variation of their line intensities. These transitions with lower energy determination represent 93.9% and 68.4% of the total absorbance in the region, at 79K and room temperature, respectively. The quality of the obtained empirical low energy values is demonstrated for CH4 by the marked propensity of the empirical low J values to be close to integers. The line lists at 79K and room temperature provided as Supplementary Material allow accounting for the temperature dependence of methane absorption between these two temperatures. The investigated region covering the 5ν 4 band of the 12CH4 isotopologue will be valuable for the theoretical treatment of this band which is the lowest energy band of the icosad. [Copyright &y& Elsevier]

Measurement of the transition of C6H+ in the gas phase near 19486 cm−1 is reported. The experiment was carried out with a supersonic slit-jet expansion discharge using cavity ringdown absorption spectroscopy. Partly resolved P lines and observation of band heads permitted a rotational contour fit. Spectroscopic constants in the ground and excited-state were determined. The density of ions being sampled is merely 2 × 108 cm−3. Broadening of the spectral lines indicates the excited-state lifetime to be ≈100 ps. The electronic transition of HC6H2 + at 26402 cm−1 assumed to be in C2v symmetry could not be rotationally resolved. [Copyright &y& Elsevier]

Optical absorption spectra of KBr:Tl+ (0.0125 mol%) single crystals shows A, B and C bands around 258, 220 and 210 nm respectively. In KCl0.1Br0.9 :Tl+ (0.0125 mol%) mixed crystals exhibit slightly broadening of the A-band towards lower wavelength side. The broadening of the absorption spectra are suggested to be due to some complex Tl+ centers involving Brand Clions formed in the mixed crystals. When excited at A, B and C-bands of Tl+ ions, PL of KBr:Tl+ showed emission band around 320 with a prominent shoulder around 365 nm. In KCl0.1Br0.9 mixed crystals the shoulder around 365 nm is not prominent due to the perturbing influence of Clions. Addition bands in the excitation spectra are attributed to the presence of Tl+ dimmers. PSL observed in X-ray irradiated crystals resembled their respective PL emissions indicating that PSL in them is due to Tl+ ions. [ABSTRACT FROM AUTHOR]

Abstract: Carbon dioxide () induced pressure broadening coefficients of water vapor () lines have been determined using a terahertz time-domain spectrometer (TDS). Thirty-two rotational transitions of were observed in the spectral range of 18– (550–3050GHz) for the first time. Using TDS allows one to measure absorption spectra with one order of magnitude better precision than Fourier transform spectrometer in this frequency region. The precision of our broadening coefficient measurements was 2.4% in average. The measured induced pressure broadening coefficients are compared to those calculated by the complex Robert–Bonamy formalism. The difference between the measurement and the theoretical estimation was in the range of to confirming the credibility of the theoretical approach. The impact on retrieval of water vapor abundance was examined by performing inversion analysis on spectra of Venus atmosphere obtained with the Submillimeter Wave Astronomy Satellite. In this example case, the retrieved water vapor mixing ratio reduces by half at the altitude region of 70–85km when applying the newly measured broadening coefficient compared to the air-broadening coefficient, and changes by 5% compared to that estimated by the complex Robert–Bonamy formalism. [Copyright &y& Elsevier]

Abstract: A sharp intense sub-Doppler feature is predicted in the probe absorption spectrum of an atomic four-level system when a hyperfine-split state interacts with a single pump. The sub-Doppler feature, which is flanked by two power-broadened transparency windows, is obtained when the frequency of the pump is greater than that of the probe, and the residual Doppler broadening is significant. [Copyright &y& Elsevier]

Abstract: Here we give a brief overview of some investigations of the gravitational microlensing influence on broad absorption spectral lines of lensed QSOs. Especially, we consider the microlensing influence on the Fe Kα broad absorption lines using a model of an accretion disk covered by an absorption region. Gravitational microlensing is modeled by ray shooting method which enables us to obtain realistic microlensing patterns. We obtain that microlensing can affect both emission and absorption component of line that depends on dimensions on emission and absorption line regions. Here we give detailed analysis of emission and absorption line shape variations due to gravitational microlensing. [Copyright &y& Elsevier]

Abstract: The absorption spectra of mixtures of methane (CH4) with N2 and O2 at different partial pressures of both CH4 and buffer gases for three temperatures 240, 267, and 296K have been recorded using the Bruker IFS 125 HR FTIR spectrometer in the 5550–6236cm−1 region. The multispectrum fitting procedure has been applied to these spectra to recover the spectral line parameters. The main goal of this procedure was the determination of the N2- and O2-broadening and shifting coefficients and the exponents of their temperature dependences. These parameters have been derived for 452 assigned lines with good values of the signal to noise ratio. The rotational dependence of the mean values of these parameters is discussed. The temperature dependence exponents were observed for both N2 and O2 buffer gases. [Copyright &y& Elsevier]

Abstract: Lorentz air-broadened half widths, pressure-induced shifts and their temperature dependences have been measured for over 430 transitions (allowed and forbidden) in the ν 4 band of 12CH4 over the temperature range 210–314K. A multispectrum non linear least squares fitting technique was used to simultaneously fit a large number of high-resolution (0.006–0.01cm−1) absorption spectra of pure methane and mixtures of methane diluted with dry air. Line mixing was detected for pairs of A-, E-, and F-species transitions in the P- and R-branch manifolds and quantified using the off-diagonal relaxation matrix elements formalism. The measured parameters are compared to air- and N2-broadened values reported in the literature for the ν 4 and other bands. The dependence of the various spectral line parameters upon the tetrahedral symmetry species and rotational quantum numbers of the transitions is discussed. All data used in the present work were recorded using the McMath–Pierce Fourier transform spectrometer located at the National Solar Observatory on Kitt Peak. [Copyright &y& Elsevier]

[Display omitted] • Measurements of H 2 O absorption spectra perturbed by Xe are performed. • Data on lines broadening and shift coefficients for (1 1 1)-(0 0 0) bands of H 2 O are presented. • A strong influence of the imaginary part of the scattering matrix on the calculated γ and δ was observed. The water vapour line broadening and shifting of 72 lines in the ν 1 + ν 2 + ν 3 vibrational band of H 2 O (in the 8603–8997 cm−1 spectral region) induced by xenon pressure were measured with a Bruker IFS HR FTIR spectrometer. These measurements were performed at room temperature, at a spectral resolution of 0.01 cm−1 and over a wide range of Xe pressure. The broadening and shift coefficients were also calculated using a semi-classical method. The intermolecular potential was taken as the sum of the anisotropic atom–atom potential and the effective vibrationally and rotationally dependent isotropic Lennard–Jones potential. The measured coefficients γ and δ were combined with data from the literature on the ν 2 , ν 1 , ν 3 , 2ν 1 + 2ν 3, 2ν 1 + 2ν 2 + ν 3 , and 3ν 1 + ν 3 bands, and optimal sets of potential parameters were found that gave the best agreement with the measured broadening coefficients. A strong influence of the imaginary part of the scattering matrix on the calculated values of the γ and δ coefficients was observed. The results were compared with those for He-, Ar-, and Kr-broadenings. The measured broadening coefficients were fitted to empirical expressions. The calculated values of the γ and δ coefficients were compared statistically to the measured values. [ABSTRACT FROM AUTHOR]

Abstract: Experimental and theoretical investigations of ozone lines broadened by nitrogen as well as oxygen have been carried out in the 300–320GHz frequency range. Lineshape analysis has demonstrated clear departures from the usual Voigt profile, actual lineshapes being narrower and higher than expected. More refined models, such as the Galatry and speed-dependent Voigt profiles, have been used. Both of them have been found to reproduce the experimental lineshapes well. However, while for the latter, the narrowing parameter shows a linear behavior with pressure, for the Galatry profile a strong nonlinear behavior is observed. Such observations demonstrate that the Dicke narrowing effect, related to molecular diffusion, cannot be the leading process involved. Experimental results have also been compared to the theoretical ones. The relaxation rate dependence on molecular speed has been computed employing the Robert–Bonamy semiclassical theory. These calculations confirm the leading role of molecular speed dependence effects. Finally, it is inferred that optical diffusion rates are much lower than the kinetic diffusion rate, a conclusion well supported from the comparison of optical and Lennard–Jones radii. [Copyright &y& Elsevier]

Abstract: We report measurements for N2-broadening, pressure-shift and line mixing coefficients for 55 oxygen transitions in the A-band retrieved using a multispectrum fitting technique. Nineteen laboratory absorption spectra were recorded at 0.02cm−1 resolution using a multi-pass absorption cell with path length of 1636.9cm and the IFS 120 Fourier transform spectrometer located at Justus-Liebig-University in Giessen, Germany. The total sample pressures ranged from 8.8 to 3004.5Torr with oxygen volume mixing ratios in nitrogen ranging between 0.057 and 0.62. An Exponential Power Gap (EPG) scaling law was used to calculate the N2-broadening and N2-line mixing coefficients. The line broadening and shift coefficients for the A-band of oxygen self-perturbed and perturbed by N2 are modeled using semiclassical calculations based on the Robert–Bonamy formalism and two intermolecular potentials. These potentials involve electrostatic contributions including the hexadecapole moment of the molecules and (a) a simple dispersion contribution with one adjustable parameter to fit the broadening coefficients or (b) the atom–atom Lennard-Jones model without such adjustable parameters. The first potential leads to very weak broadening coefficients for high J transitions whereas the second potential gives much more improved results at medium and large J values, in reasonable agreement with the experimental data. For the line shifts which mainly arise in our calculation from the electronic state dependence of the isotropic potential, their general trends with increasing J values can be well predicted, especially from the first potential. From the theoretical results, we have derived air-broadening and air-induced shift coefficients with an agreement comparable to that obtained for O2–O2 and O2–N2. [Copyright &y& Elsevier]

Rapid passage signals exhibiting saturation effects have been observed when a low-pressure sample of ethylene, within a multiple pass absorption cell, is subjected to radiation from a repetitively pulsed 10.25  micron quantum-cascade laser. Within each pulse the laser frequency sweeps 36  GHz from high to low frequency in a time of 140  ns. At the low gas pressures, less than 20  mTorr, in the absorption cell the sweep rate through a Doppler-broadened absorption line (ca. 0.5  ns), is much faster than the collisional relaxation time of the ethylene and this leads to rapid passage effects. Examples are given of the complex rapid passage signals observed in pure and nitrogen broadened spectra. The rapid passage effects, which lead to the variety of the observed signals, have been modelled by numerical solution of the coupled Maxwell–Bloch equations for four sets of two-level systems. [ABSTRACT FROM AUTHOR]

For absorption lines, the distortion of spectral lines by experimental spectrometers must be considered in measuring linewidth which has been investigated by many authors. While in the derivative spectrum, we managed to give the corrections of instrumental broadening and distortion to obtain accurate linewidths. We developed a universal fitting program which was explored together with the method of correction in the fundamental band spectra of LMR of NO. The uncorrected halfwidths were compared with the corrected values, which were obtained from the program. The results of comparison are very satisfactory and demonstrate their useful application to analyze experimental spectra. [ABSTRACT FROM AUTHOR]

Abstract: The near-infrared absorption spectrum of He2 has been recorded in the range of 12090–13300cm−1 using the optical heterodyne concentration modulation spectroscopy. Fifty-nine He2 spectral lines were assigned to the (1,0), (2,0), (3,1) and (4,2) bands in the c 3Σg +–a 3Σu + system and a non-linear least-squares fitting was performed to get the improved molecular constants for the levels (υ =1, 3 and 4) in the upper electronic state. [Copyright &y& Elsevier]