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A low resolution (0.5 cm−1) Fourier transform infrared (FTIR) spectrum of 13C2D4 in the 2000–4800 cm−1 region was recorded to re-analyze the two fundamental bands ( ν 9 and ν 11 ) and to identify the combination bands in this region. The combination bands ν 2 + ν 12 , ν 6 + ν 11 , ν 6 + ν 9 , ν 1 + ν 12 , ν 5 + ν 12 , ν 2 + ν 11 , ν 2 + ν 9 , ν 5 + ν 11 and ν 5 + ν 9 were identified and their band centers (with an uncertainty of ± 0.1 cm−1) and band types were determined. In addition, the high-resolution FTIR spectrum of the fundamental ν 11 band (2120–2250 cm−1) was recorded at an unapodized resolution of 0.0019 cm−1 and its infrared (IR) lines were analyzed. Rovibrational constants up to five quartic terms and band center of 2193.75943(22) cm−1 were derived with improved precision for the ν 11 = 1 state, with an rms deviation of 0.0019 cm−1. Three rotational constants and the band center of the ν 2 = ν 7 = 1 state together with the b-Coriolis resonance parameter were derived with improved precision from the study of the Coriolis interactions between the two states ( ν 11 = 1 and ν 2 = ν 7 = 1 ). Also in this work, the FTIR spectrum of the ν 9 band of 13C2D4 was measured between 2230 and 2450 cm−1 at an unapodized resolution of 0.0019 cm−1. For the first time, 2069 perturbed and unperturbed IR transitions of the ν 9 band, centered at 2324.358484(46) cm−1, were fitted to obtain the a-Coriolis resonance parameter from its interaction with the ν 4 = ν 10 = ν 12 = 1 state. The IR lines of the ν 4 + ν 10 + ν 12 band were too weak for detection. Two rotational constants (A and B), the band center of the ν 4 + ν 10 + ν 12 band and the a-type Coriolis resonance parameter were derived for the first time in this work. All the rotational constants A, B and C for the ν 11 , ν 9 and ν 2 + ν 7 bands are in close agreement with theoretically calculated values using the cc-pVQZ basis set at MP2 and B3LYP levels of theory. Ground state rovibrational constants of 13C2D4 up to three sextic terms were also derived from a fit of 3153 ground state combination differences (GSCDs) with an rms deviation of 0.00037 cm−1 from the IR transitions of the present analyses.

We have observed twelve triplets of two Lamb dips and a crossover signal in Stark spectroscopy of the ν 3 band of methane using a comb-referenced sub-Doppler resolution spectrometer. The crossover signal consists of two crossover resonances in the Λ - and V-type three-level systems, which overlap each other in frequency under the first-order Stark shifts (Tyurikov et al., 1997). The intensity of the crossover signal relative to the Lamb dips agrees well with a simple calculation based on steady-state solutions of rate equations in weak saturation using the observed intensity ratio of the Lamb dips in the Λ -type three-level system.

International audience; Resolved laser induced fluorescence spectra of 58NiD, recorded at Doppler resolution between 11000 and 18000 cm-1 have established more than 200 term energies in two of the three strongly interacting, low-lying states (2Δ, 2Π, 2Σ+) of NiD, associated with an Ni+(3d9)D- configuration. Our observations span v= 0-5 in the lowest spin-orbit component of the ground state, X 2Δ5/2, v = 0-3 in X 2Δ3/2 and v = 0-1 in the lower component of the W 2Π3/2 state. Collisional processes populate several neighbouring excited states, allowing us also to locate the first rotational levels of A(Ω = 5/2) v = 1, I(Ω = 3/2) v = 0 and E(Ω = 3/2) v = 1 at 16664.8, 17367.3 and 17508.1 cm-1 respectively. Spin-orbit and rotation-electronic interactions are strong in NiD (as in NiH), and with no direct observation of either of the Ω" =1/2 states, meaningful representations of the low-lying energy levels is difficult. We have therefore attempted a global, multi-isotope fit to reproduce the term energies of the known term energies of NiD and 58,60,62NiH (where some Ω" =1/2 levels are known). Dunham-type parameters have been used to represent the unperturbed 2Δ, 2Π and 2Σ+ states, with off-diagonal matrix elements (treating spin-orbit, L- and S-uncoupling effects) based on Ni+ atomic properties. Born-Oppenheimer breakdown terms were included in the model. The equilibrium bond lengths for 58NiH/58NiD are 1.4545(1)/1.4559(1) Å for the X 2Δ state and 1.5094(2)/1.5083(2) Å for the W 2Π state.

We report high resolution Fourier Transform Infrared (FTIR) spectra of nitrogen trifluoride (trifluoroamine, NF3) measured with the Zurich Bruker prototype spectrometer (ZP 2001) and the SLS THz/FTIR setup (2009 prototype) in the range 20–3000 cm - 1 at temperatures between 80 and 120 K using a collisional cooling cell designed with White cell multipath reflection optics and at room temperature (296 K). Except in the far-infrared with instrument limited resolution ( Δ ν FWHM = 0.0008 cm - 1 ) many of the spectra are nearly Doppler limited. Rovibrational transitions were assigned to 13 different vibrational bands and were used then in the fitting procedure. We re-investigated the bands 2 ν 4 , ν 1 , ν 2 + ν 4 , ν 1 + ν 4 , 2 ν 3 and ν 1 + ν 3 , which had been studied before, and we have analyzed the ν 2 + ν 3 , 2 ν 1 , ν 1 + ν 2 + ν 4 , ν 1 + ν 2 + ν 3 , ν 2 + 2 ν 3 , 3 ν 3 , ν 1 + 2 ν 3 bands for the first time. All our analyses refer to the isotopomer 14 NF3.

The 2ν6 (A1 + E)/ν2 + ν3 (A1)/ν3 + ν5 (E) band system of CH3Br, near 2000 cm−1, has been studied, for both 79Br and 81Br isotopologues, using Fourier transform infrared spectroscopy, with a resolution of 0.003 cm−1. This band system, revealing anharmonic (Δk = Δl = 0) and Coriolis (Δk = Δl = ± 1) interactions, has been analyzed through a least-squares fit of more than 3000 transitions, for each isotopologue. More than 600 transitions belonging to the very weak ν3 + ν5 combination band were assigned for the first time, for both CH379Br and CH381Br isotopologues. Assignments of the weak 2 ν 6 0 parallel band, which is Fermi-interacting with ν2 + ν3, were also considerably extended with respect to a previous high-resolution study (Najib et al., 1985), thanks to a more accurate knowledge of the Fermi coupling parameters and of the relative positions of the interacting levels. The least-squares fits provided quantitative reproduction of all data belonging to the four above mentioned bands. Moreover, the Coriolis coupling parameters obtained for the ν2 + ν3/ν3 + ν5 interacting bands show a remarkable consistency with those obtained for the ν2/ν 5 ‘fundamental’ system (Kwabia Tchana et al., 2004).

The IR absorption spectra of pure carbon dioxide in the region of the forbidden ν2 + ν3 vibrational transition at 3004 cm−1 have been recorded using a Fourier-transform spectrometer. A multipass-optical cell with the path length of 100 m was used in the study. The data were taken at room temperature of 294.8 K with a resolution of 0.02 cm−1 over the spectral region 2500–3500 cm−1. A sample pressures varied from 207 to 463 kPa (2.04–4.57 atm). The measured binary absorption coefficients provide the band integrated intensity value of (2.39 ± 0.04) ∗ 10−4 cm−2 amagat−2. The result is compared with those from previous works. The observed band profile features are discussed.

The high-resolution Fourier transform spectrum of propyne-d3 (CD3CCH) at room temperature has been recorded in the region of the ν7 band (950–1200 cm−1) at an apodized resolution of 0.004 cm−1. About 2400 lines consisting of a total of 25 sub-bands ranging from KΔK = −13 to 12 have been assigned in the ν7 band of CD3CCH. In the fitting analysis, the ν4 = 1 state to which transitions have not been identified in the experimental spectrum included as a “shadow” state. The data have been analyzed taking into account of the strong x-y Coriolis interaction of the ν7 = 1 state with the ν4 = 1 state. l-type interactions between the ± l components of the ν7 = 1 state, and a weak k-type doubling interaction between ν7 = 1 and ν4 = 1 states have been included in the analysis. The vibration-rotation transitions for K ≥ 8 show fairly large amount of deviation and most likely interacted by other nearby states. The transitions upto K = 7 and Jmax = 61 could be fitted with a standard deviation of 0.0007 cm−1.

International audience; VUV photoionization dynamics of the S2 molecule were re-investigated from threshold up to 15.0 eV, using synchrotron radiation coupled with double imaging photoelectron/photoion coincidence featuring high resolution capabilities. We measured the first threshold photoelectron spectrum of S2 achieving higher resolution than previous literature to derive accurate spectroscopic constants for a few electronic states of the cation including the X 2 PW, g ground state and the a 4 Pu, b 4 Sg-, and B 2 Sgstates. We also recorded the total ion yield for S2 up to a photon energy of 15.0 eV which, combined with the threshold photoelectron spectrum, led to the assignment of various autoionizing Rydberg series.

A Fourier transform spectrum of sulfur dioxide 33S16O2 has been recorded in the 18.3 μm spectral region at a resolution of 0.002 cm−1 using a Bruker IFS 125HR spectrometer leading to the observation of the ν2 and 2ν2-ν2 vibrational bands of the 33S16O2 molecule. The corresponding upper state ro-vibrational levels were fit using Watson-type Hamiltonians. In this way it was possible to reproduce the upper state ro-vibrational levels to within the experimental uncertainty; i.e., ∼0.20 × 10−3 cm−1. Very accurate rotational and centrifugal distortion constants were derived from the fit together with the following band centers: ν0 (ν2) = 515.659089(50) cm−1, ν0 (2ν2) = 1030.697723(20) cm−1.

We present a high resolution spectroscopic study on the B1A′ – X1A′ 000 electronic origin band of CuSH near 434 nm. The CuSH molecules are produced by a corona discharge of a H2S/Ar gas mixture with copper needle electrodes in a supersonic jet expansion. The high-resolution spectrum of the B1A′ – X1A′ 000 band of jet-cooled CuSH are recorded by laser induced fluorescence with a spectral resolution of ∼0.02 cm−1. From a detailed rotational analysis of the experimental spectrum, accurate spectroscopic constants of the B1A′ state are determined for both 63CuSH and 65CuSH isotopologues.

The high-resolution Fourier transform infrared (FTIR) spectrum of formaldoxime-13C (13CH2NOH) was recorded in the 840–930 cm−1 region with an unapodized resolution of 0.0019 cm−1 for a rovibrational analysis. In the analysis of the dominantly A-type ν 8 band, a total of 1025 infrared transitions were fitted using the Watson's A-reduced and S-reduced Hamiltonians in the Ir representation with a root-mean-square (rms) deviations of 0.000430 cm−1 and 0.000431 cm−1 respectively. From the rovibrational analysis, the ν 8 = 1 states rotational constants (A, B and C), five quartic terms (ΔJ, ΔJK, ΔK, δJ, δK) and one sextic term (ΦKJ) were derived for the first time. The band center of the ν 8 band of 13CH2NOH was found to be 890.235170(25) cm−1 and 890.235182(25) cm−1 in the A-reduced and S-reduced Hamiltonians respectively. Ground state rovibrational constants except for rotational constants B and C were obtained for the first time through the fitting of 443 ground state combination differences (GSCDs) derived from the infrared transitions of the ν 8 band of 13CH2NOH, together with 2 previously reported microwave frequencies. The rms deviation of the GSCD fits was the same at 0.000430 cm−1 for both A-reduced and S-reduced Hamiltonians. Furthermore, rovibrational constants up to 5 quartic centrifugal distortion terms of the ground state, and the band center and rotational constants (A, B and C) of the ν 8 = 1 state were computed from theoretical anharmonic calculations at two different levels of theory, B3LYP and MP2 with the cc-pVTZ basis set. Good agreement was found between the experimental and calculated rovibrational constants of 13CH2NOH for both ground and ν 8 = 1 states.

The high resolution vibrational spectrum of vinyl acetylene (C2H3CCH) has been investigated in the far infrared region from 180 to 360 cm−1 using the Bruker IFS 120 HR spectrometer at Justus-Liebig-Universitat, Giesen, Germany. The two energetically lowest vibrational fundamentals ν13 and ν18 at 214 cm−1 and 304 cm−1, respectively, were measured at a resolution of 0.0016 cm−1. In addition to the fundamental modes, several hot bands originating from either ν13 or ν18 were observed and analyzed. The spectroscopic analysis was supported by high-level quantum-chemical coupled-cluster calculations and also made use of the Automated Spectral Line Assignment Procedure, ASAP, outlined earlier (Martin-Drumel et al., 2015). In addition to the infrared study, so far unpublished millimeter-wave vibrational satellites that were measured in the course of an earlier study of the pure rotational spectrum of vinyl acetylene in its ground vibrational state (Thorwirth and Lichau, 2003) were added to the data set and are reported here for the first time.

Several bands in a new electronic transition of tungsten sulfide, WS, have been recorded at Doppler-limited resolution using intracavity laser spectroscopy with Fourier-transform detection (ILS-FTS). WS molecules were produced in the plasma discharge of a W-lined Cu hollow cathode in the presence of a gas mixture containing approximately 70% Ar and 30% H2, with a trace amount of CS2 at a total pressure of 1 torr. The (0,0), (1,0), (2,0), (1,1), (2,1), and (3,1) bands of the [15.05]0+ – X 3Σ–(0+) transition of WS were observed. Line positions for the four major isotopologues (182W32S, 183W32S, 184W32S, and 186W32S) of the (0,0), (1,0), and (2,0) bands were used in the fit. The WS bands were analyzed using PGOPHER, with previously determined constants for the X 3Σ–(0+) ground state [Harms et al., J. Mol. Spectrosc. 374, 111,378 (2020)] held fixed in the fit. A perturbation was observed in the (0,0) band which appears to be caused by an electronic state that has not been observed. Molecular parameters for the newly identified excited state are presented.

Transmission spectra of CO 2 highly diluted in water vapor have been recorded at 50 and 95 °C for four pressures between 0.02 and 0.1 atm using a high resolution Fourier Transform spectrometer. The collisional (Lorentz) widths of many lines of the ν 3 band (and of some of the ν 3 + ν 2 − ν 2 hot band) have been retrieved from each spectrum through fits using Voigt line shapes. Our result are about 4% lower than the values recommended in a previous study but they confirm the relative variations of the line broadening on the rotational quantum numbers. We also provide the first determination of H 2 O-induced line shifts of CO 2 lines.

Perdeutero-spiropentane (C 5 D 8 ) has been synthesized, and infrared and Raman spectra are reported for the first time. Wavenumber assignments are made for most of the fundamental vibrational states. Gas phase infrared spectra were recorded at a resolution (0.002 cm −1 ) sufficient to resolve individual rovibrational lines and show evidence of strong Coriolis and/or Fermi resonance interactions for most bands. However a detailed rovibrational analysis of the fundamental ν 15 ( b 2 ) parallel band proved possible, and a fit of more than 1600 lines yielded a band origin of 1053.84465(10) cm −1 and ground state constants (in units of cm −1 ): B 0 = 0.1120700(9), D J = 1.51(3) × 10 −8 , D JK = 3.42(15) × 10 −8 . We note that the B 0 value is significantly less than a value of B a = 0.1140 cm −1 calculated using structural parameters from an earlier electron diffraction (ED) study, whereas one expects B a to be lower than B 0 because of thermal averaging over higher vibrational levels. A similar discrepancy was noted in an earlier study of C 5 H 8 (Price et al., 2011). The structural and spectroscopic results are in good accord with values computed at the anharmonic level using the B3LYP density functional method with a cc-pVTZ basis set.

The Fourier transform infrared (FTIR) spectrum of formaldoxime (CH2NOH) was recorded in the 700–3800 cm−1 region at the Australian Synchrotron with an unapodized resolution of 0.5 cm−1 to identify its fundamental and overtone bands and to measure their relative infrared (IR) intensities in this region. The high-resolution FTIR spectrum of the ν 9 band of CH2NOH was also recorded with an unapodized resolution of 0.00096 cm−1 in the 450–600 cm−1 region for a rovibrational analysis. In the analysis of the A/B-hybrid type ν 9 band, a total of 2011 infrared transitions (1655b-type and 356 a-type transitions) were fitted using the Watson's A-reduced and S-reduced Hamiltonians in the Ir representation with a root-mean-square (rms) deviation of 0.000096 cm−1 and 0.000305 cm−1 respectively. From this rovibrational analysis, the v 9 = 1 state rotational constants (A, B and C) and five quartic terms (ΔJ, ΔJK, ΔK, δJ, δK) were improved from previous work and three sextic terms (ΦJK, ΦKJ, ΦK) were derived for the first time. The band center of the ν 9 band of CH2NOH was found to be 530.0187764(63) cm−1 and 530.018762(18) cm−1 in the A-reduced and S-reduced Hamiltonians respectively. All five quartic and three sextic (ΦJK, ΦKJ, ΦK) centrifugal distortion terms of the ground state of CH2NOH were also improved with higher accuracy. They were obtained through the fitting of 3020 ground state combination differences (GSCDs) derived from the IR transitions of the ν 9 , ν 12 and ν 10 bands of CH2NOH, together with 23 previously reported microwave frequencies. The rms deviation of this GSCD fit was 0.000498 cm−1 and 0.000519 cm−1 in the A-reduced and S-reduced Hamiltonians respectively. Additionally, rotational constants and higher order centrifugal distortion terms of the ground and v 9 = 1 states were computed from theoretical anharmonic calculations at two different levels of theory, B3LYP and MP2 with the cc-pVTZ basis set, for comparison with the experimental results. The calculated and experimental rovibrational constants of CH2NOH for both ground and v 9 = 1 states were in good agreement.

A high-resolution broadband study of the methanol absorption spectrum was performed at 1.480–1.495 THz. The transmittance was recorded under both self- and air-broadening conditions for multiple pressures at a resolution of 500 kHz. A multispectral fitting analysis was then performed. The transition frequency, absolute intensity, self- and air-broadening coefficients, and self- and air-induced pressure shifts were retrieved for 221 absorption lines using the multispectral fitting routine. Observed in the data were two different series of transitions, both a b-type Q-branch with K = - 7 ← - 6 and an a-type R-branch with J = 31 ← 30 . The retrieved frequency position values were compared with values from spectral databases and trends within the different series were identified. An analysis of the precision of the fitting routine was also performed.

We performed Doppler-free two-photon absorption spectroscopy of naphthalene using an optical frequency comb as a frequency reference. Rotationally resolved rovibronic spectra were observed, and absolute frequencies of the rovibronic transitions were determined with an uncertainty of several tens of kHz. The resolution and precision of our system are finer than the natural width of naphthalene. We assigned 1466 lines of the Q ( K a ) Q ( J ) transition and calculated molecular constants. We attribute systematic spectral line shifts to the Coriolis interaction, and discuss the origin of the spectral linewidths.

We report the Fourier Transform Infrared (FTIR) spectrum of chlorobenzene (C6H5Cl) measured using synchrotron radiation and the ETH-SLS 2009 prototype spectrometer at the Swiss Light Source (SLS). The maximum optical path difference of these measurements was 11.8 m leading to a resolution of better than 0.0008 cm−1. The spectra were taken at room temperature in the range 600–900 cm−1. It was possible to analyze the in-plane mode ν 12 of A 1 symmetry ( ν 0 = 706.6686 cm−1) and the out-of-plane mode ν 10 b of B 1 symmetry ( ν 0 = 741.2240 cm−1) of C6H535Cl. In addition, the ground state constant Δ K of C6H535Cl has been readjusted using combination differences (CD).

The high-resolution rotationally resolved Fourier-transform infrared spectrum of the NO2 in-plane rock band (440–510 cm−1) of nitromethane (CH3NO2) has been recorded using the Far-Infrared Beamline at the Canadian Light Source, with a resolution of 0.00096 cm−1. About 1773 transitions reaching the upper state levels m ′ = 0 ; K a ′ ⩽ 7 ; J ′ ⩽ 50 have been assigned using an automated ground-state combination difference program together with the traditional Loomis–Wood approach. These data from the lowest torsional state, m′ = 0, were fit using the six-fold torsion-rotation program developed by Ilyushin et al. (2010). The analysis reveals that the rotational energy level structure in the upper vibrational state is similar to that of the ground vibrational state, but the sign and magnitude of high-order constants are significantly changed suggesting the presence of multiple perturbations.

A high resolution (0.0015 cm −1 ) IR spectrum of propane, C 3 H 8 , has been recorded with synchrotron radiation at the French light source facility at SOLEIL coupled to a Bruker IFS-125 Fourier transform spectrometer. A preliminary analysis of the ν 21 fundamental band (B 1 , CH 3 rock) at 921.382 cm −1 reveals that the rotational energy levels of 21 1 are split by interactions with the internal rotations of the methyl groups. The AA, EE and AE + EA components of this A-type band have their band centers at 921.3724(38), 921.3821(33) and 921.3913(44) cm −1 , respectively. These torsional splittings most probably are due to anharmonic and/or Coriolis resonance couplings with nearby highly excited states of both internal rotations of the methyl groups. In addition, several vibrational–rotational resonances were observed that affect the torsional components in different ways.

In the first observed spectrum (Melville and Coxon, 2001) of the 000 – 000 band of the A 2 Π 1 / 2 - X 2 Σ + transition of YbOH, spin-doublets were resolved only at high-N and yielded a ground state spin-rotation constant, γ, that differs in both sign and magnitude from that obtained from recent higher resolution low–N data (Steimle and co-workers, 2018–2019). This note re-examines the original 2001 data and shows that the discrepancy is resolved by rearrangement of the original Q11 and R12 branch and isotopologue assignments of the 000 – 000 origin band. Re-analysis of the 000 – 100 band results in a revised negative γ for the υ1 = 1 (Yb-O stretch) level of the X 2 Σ + state which is close to that obtained from the 2018–2019 data.

Experimental absorption cross-section spectra of HFE-356mec3 (CH3OCF2CHFCF3) have been acquired at three temperatures and at a resolution of 0.1 cm−1 over the spectral range 550–3500 cm−1. The results have been completed with theoretical calculations using density functional theory and ab initio methods at different levels of theory. A lifetime-corrected radiative efficiency of 0.31 Wm−2ppb−1 was obtained, leading to a 100-year time horizon global warming potential of 260 using an atmospheric lifetime of 2.5 years.

Sub-Doppler resolution spectroscopy of the fundamental vibration bands of H 35 Cl and H 37 Cl has been carried out from 87.1 to 89.9 THz. We have determined the absolute transition frequencies of the hyperfine-resolved R (0) to R (4) transitions with a typical uncertainty of 10 kHz. We have also yielded six molecular constants for each isotopomer in the vibrational excited state, which reproduce the determined frequencies with a standard deviation of about 10 kHz.

The absorption spectrum of sodium iodide vapor between 200 and 275 cm −1 has been measured with a resolution of 0.006 cm −1 at a temperature of 1096 K. The Δ v = 1 transitions from v = 1 ← 0 to v = 13 ← 12 have been measured. Dunham constants are given from an least-squares analysis of 1285 fairly well resolved transitions. The band center for the fundamental band is ν 0 = 257.2837 ± 0.0002 cm −1 . The relative intensities of the Δ v = 1 transitions from different vibrational states are studied and it is shown that the intensity is roughly proportional to v ″ + 1 as expected from the harmonic oscillator approximation. From measurements of the Herman–Wallis constant, α 1,0 = −0.0054 ± 0.0008, it is estimated that the transition moment must be μ 1,0 ≈ 0.135 ± 0.020 debye.

The Fourier transform infrared (FTIR) absorption spectrum of the ν 12 fundamental band of ethylene- d 4 (C 2 D 4 ) was recorded in the 1000–1150 cm −1 region with a resolution of 0.00096 cm −1 using the THz/far-infrared beamline of the Australian Synchrotron. Upper state ( ν 12 = 1) rovibrational constants consisting of three rotational constants and up to five quartic constants were improved by assigning and fitting 3950 rovibrational transitions using Watson’s A -reduced and S -reduced Hamiltonians in the I r representation. The band centres of the unperturbed A -type ν 12 band are found to be 1076.984958(14) cm −1 and 1076.984813(14) cm −1 for A -reduced and S -reduced Hamiltonians respectively. The present analysis, covering a wider wavenumber range and higher J and K c values (up to 58) than previous studies, yielded upper state constants including the band centre which are more accurate than previously reported. The rms deviation of the upper state ( ν 12 = 1) fit is 0.00040 cm −1 in the A -reduction and 0.00041 cm −1 in the S -reduction. Improved ground state rovibrational constants were also determined from the fit of 3151 ground state combination differences (GSCD) from the presently-assigned transitions of the ν 12 band of C 2 D 4 using Watson’s A -reduced and S -reduced Hamiltonians in the I r representation. The rms deviation of the GSCD fit is 0.00036 cm −1 in the A -reduction and 0.00035 cm −1 in the S -reduction. The ground state constants of C 2 D 4 derived from the experimental GSCD fit are in good agreement with those from theoretical calculations using the B3LYP/cc-pVTZ, MP2/cc-pVTZ, and CSSD/cc-pVTZ levels, up to five quartic constants.

The high-resolution Fourier transform spectrum of methyl acetylene-d 1 (CH 3 CCD) at room temperature has been recorded in the region of the ν 3 band (1980–2035 cm − 1 ) at an apodized resolution of 0.004 cm − 1 . About 600 vibration–rotation transitions have been assigned, with J upto 36 and K upto 6. The spectrum shows the presence of several perturbations. The observed minus calculated deviation of the fit for K = 4 subband is much more than the expected, shows the presence of Fermi resonance with the nearby vibrational state.

The rotational spectra of two isotopic species of hydrogen sulfide have been revisited. For H 2 33 S, which was detected in natural abundance, accurate measurements were performed in the submillimeter-wave region, from 500 GHz up to 1.56 THz, thus allowing improvement of the spectroscopic parameters as well as determination of new high-order centrifugal-distortion constants. The rotational spectrum of the main isotopologue was investigated in the millimeter- and submillimeter-wave region up to 1.6 THz, employing the Lamb-dip technique to obtain sub-Doppler resolution. As a consequence, transition frequencies at 1 THz were retrieved with an accuracy of 1 kHz and the hyperfine structure due to hydrogens was resolved, thus allowing the first determination of the spin–rotation tensor of H in H 2 S. Improved and new spectroscopic parameters were then provided that allow accurate predictions of rotational transitions up to 20 THz; in particular, the newly determined constants permit prediction of rotational transitions with J K a 12 (up to about 10 THz) with expected uncertainties of a few hundreds of kHz.

The near-infrared (NIR) emission spectrum of H 12 C 15 N was measured in the 6050–6500 cm −1 range at a resolution of 0.044 cm −1 using an emission setup available at the Justus-Liebig Universitat, Giessen, Germany. The rich emission spectrum showing numerous overlapped spectral profiles was analyzed with the spectrum analysis software SyMath running using Mathematica as a platform. This approach allowed us to retrieve the vibrational–rotational constants for 32 bands. Many spectroscopic transitions have been observed for the first time in a lab environment. We quantified four newly observed Coriolis resonances.

Absolute individual line intensities of numerous transitions of the fundamental ν 2 and ν 10 bands of oxirane (ethylene oxide, cyc-C 2 H 4 O) have been measured in the 1420–1560 cm −1 region using seven high-resolution Fourier transform spectra recorded at 0.002 cm −1 resolution and various pressures. These line intensities were least-squares fit using a theoretical model which takes into account the vibration–rotation interactions linking the upper state rotational levels, and, therefore, accurate rotational expansion of the transition moments of the ν 2 and ν 10 vibrational bands were derived. Using the coefficients obtained in the fitting, a line list of both bands has been generated. Comparisons with measurements taken at low resolution of the ν 2 / ν 10 dyad system show excellent agreement.

The 2v(1) (A(1)) Si-H stretching overtone band of HSiD3 has been recorded at a resolution of ca. 0.009 cm(-1) between 4200 and 4400 cm-1. About 790 ro-vibration transitions of the (HSiD3)-Si-28 isotopologue have been assigned, with! up to 24 and K up to 21. The spectrum evidences the existence of several perturbations. The assigned transitions have been analyzed either neglecting or including in the model A(1)/E Coriolis-type interactions between v(1) = 2 and nearby dark states. The standard deviation of all the fits is, however, more than one order of magnitude larger than the estimated experimental precision and is independent of the adopted model. (C) 2012 Elsevier Inc. All rights reserved.

Emission spectra of the A 2 Π → X 2 Σ + and B 2 Σ + → X 2 Σ + transitions of CaD were produced in a discharge-furnace emission source and recorded with a high resolution Fourier transform spectrometer. The Δ v = 0 and Δ v = −1 sequences up to v′ = 3 of the A 2 Π state and v′ = 2 of the B 2 Σ + state have been observed and rotationally analyzed. Empirical band constants and Dunham-type constants were determined for all electronic states using N 2 Hamiltonians. The equilibrium constants T e , ω e and ω e x e were determined to be 14407.604(2), 957.330(4) and 10.415(2) cm −1 for the A 2 Π state, and 15751.570(2), 925.840(4) and 12.417(2) cm −1 for the B 2 Σ + state, respectively. The equilibrium bond lengths ( r e ) of the A 2 Π and B 2 Σ + states are 1.977495(3) and 1.963467(6) A, respectively.

The far infrared spectrum of the four-membered heterocycle 3-oxetanone (c-C 3 H 4 O 2 ) has been recorded in the region 100–200 cm −1 with a resolution of 0.000959 cm −1 using synchrotron radiation from the Canadian Light Source. The ring puckering mode (ν 21 ) and first three hotbands were observed and 9165 separate rovibrational transitions were assigned and analyzed. The band centers of the fundamental band (139.549148(5) cm −1 ) and first three hotbands (v = 1 → v = 2: 141.093457(14) cm −1 , v = 2 → v = 3: 142.644034(19) cm −1 and v = 3 → v = 4: 143.989670(26) cm −1 ) were accurately determined for the first time along with the rotational and centrifugal distortion constants that characterize the four excited vibrational states. Based on our spectra, the potential governing this vibrational mode of 3-oxetanone has the form of V = ax 4 + bx 2 (where a = 2.04388 × 10 5 cm −1 /A 4 and b = 4.26392 × 10 4 cm −1 /A 2 ) along the ring puckering coordinate x .

The ν4 fundamental band (CO2 antisymmetric stretching mode) of the FCO2 radical in the ground electronic state X ˜ 2 B 2 has been recorded by Fourier-transform infrared spectroscopy at an effective resolution of 0.003 cm−1 between 1040 and 1130 cm−1. FCO2 was generated by vacuum flash pyrolysis at about 350 °C of FC(O)OO(O)CF. More than 3300 ro-vibrational transitions have been assigned, which involved levels with N′ up to 56 and K a ′ up to 38. The observed Doppler-broadened spectrum was analyzed to yield accurate values of the band origin (1094.142210(27) cm−1, one standard error in parentheses), the rotational constants, the quartic centrifugal distortion constants and electron spin-rotation interaction parameters in the v4 = 1 state. Large variations of the centrifugal distortion parameters ΔK (+26%), ΔNK (−1463%) and δK (−10%) upon excitation of the ν4 vibration have been observed.

The first air broadening line shape parameters were determined for the 2 ← 0 bands of 13C16O near 4166.8 cm−1 and 12C18O near 4159.0 cm−1. Air-broadened Lorentz half-width coefficients, their temperature dependence exponents; air-induced pressure shift coefficients, their temperature dependences; and air line mixing coefficients were measured. Additionally, speed-dependent line shapes with line mixing employing the off-diagonal relaxation matrix element coefficients were applied to minimize the fit residuals. Finally, individual line positions and line intensities of the two isotopologues were constrained to the well-known theoretical quantum mechanical expressions in order to obtain the rovibrational (G, B, D and H) and band intensity parameters (including Herman–Wallis coefficients). For this, laboratory spectra were recorded at 0.005 cm−1 resolution using a temperature-controlled coolable absorption cell configured inside a Bruker IFS 125HR Fourier transform spectrometer. Gas temperatures and pressures for the spectra varied from 150 to 298 K and 20 to 700 Torr, respectively. Results were obtained from broad-band multispectrum least-squares fitting of the 4000–4360 cm−1 spectral region. Four isotope-enriched pure sample spectra and twelve spectra with air + CO samples (13C16O or 12C18O, as appropriate) were fitted simultaneously. The results obtained for 13C16O and 12C18O are compared and discussed.

The degenerate combination level ν3 = ν5 = 1 (1669.09 cm−1, E symmetry) was investigated with high-resolution, using a Fourier-transform infrared spectrum recorded in the 1600–1800 cm−1 region, at a resolution of 0.0024 cm−1. A second spectrum, recorded in the 900–1100 cm−1, at a resolution of 0.0024 cm−1, was employed to analyze the ν3 + ν5 − ν3 hot band. The studied combination level has to be treated as a part of a polyad including two other dark states: (ν3 = 1, ν6 = 2, l6 = 0, ∓ 2) and (ν4 = ν6 = 1). The important anharmonic, Coriolis, and α-resonance interactions were extrapolated from the previously studied dyads ν5/2ν6 and ν4/ν3 + ν6. The reproduction thus achieved is quantitative for all the assigned data and provides spectroscopic parameters which are consistent with those of the system of vibrational levels ν5/2ν6.

The pure rotational spectrum of benzanthrone an oxygenated polyaromatic hydrocarbon has been recorded and assigned in the region 7–61 GHz. An initial analysis, guided by ab initio molecular orbital predictions, of frequency-scanned Stark modulated, jet-cooled millimeter wave absorption spectra (48–87 GHz) yielded a preliminary set of molecular constants. Subsequent spectral analysis at higher resolution was carried out with Fourier Transform Microwave (FT-MW) spectroscopy (13–18 GHz) of a supersonic rotationally cold molecular expansion. The high spectral resolution of the FT-MW instrument provided an improved set of molecular constants. Density Functional Theory (DFT) calculations at the B3LYP/6-311+G ** level of theory closely predict the experimental rotational and centrifugal distortion constants.

Rotational structure in the 28 0 1 fundamental band of isobutylene has been examined at room temperature using a combination of FTIR and Pb-salt diode laser instruments. The highest spectral resolution for the FTIR measurements was 0.125 cm−1. Even at this resolution however, rotational structure for the 28 0 1 band could be observed and appeared to possess a very regular pattern. A preliminary spectral assignment was obtained using the Watson/Gora asymptotic approximation for a rigid oblate asymmetric rotor. Within this approximation, the 28 0 1 band origin was determined to be 890.937 (4) cm−1. Excited state rotational constants, without the inclusion of centrifugal distortions terms, are A = 0.3033(16), B = 0.2801(12) and C = 0.15362 (8) cm−1 respectively. Finally, a full set of spectroscopic constants, including quartic centrifugal distortion constants, were obtained for the 28 0 1 band by including the high resolution Pb-salt spectra.

The microwave spectra of gaseous 1-fluoronaphthalene and 2-fluoronaphthalene have been measured using three different Fourier transform microwave spectrometers in the frequency range of 1.8–10 GHz, with substantial improvements in resolution over previous measurements. The measurements include 15 a-dipole and 15 b-dipole transitions for 1-fluoronaphthalene and 12 a-dipole and 16 b-dipole transitions for 2-fluoronaphthalene. Analysis of measured lines for 1-fluoronaphthalene has yielded ground state rotational constants of A = 1920.581(2) MHz, B = 1122.2370(5) MHz, and C = 708.4819(3) MHz. Analysis of the 2-fluoronaphthalene spectra has yielded rotational constants of A = 2844.761(2) MHz, B = 808.1592(8) MHz, and C = 629.5032(3) MHz. Calculated (G09) rotational constants are in very good agreement with measured values.

Rotationally resolved vibrational spectra of the three lowest frequency bands of the four-membered heterocycle azetidine (c-C 3 H 6 NH) have been collected with a resolution of 0.00096 cm −1 using the far infrared beamline at the Canadian Light Source synchrotron. The modes observed correspond principally to motions best described as: β-CH 2 rock ( ν 14 ) at 736.701310(7) cm −1 , ring deformation ( ν 15 ) at 648.116041(8) cm −1 , and the ring puckering mode ( ν 16 ) at 207.727053(9) cm −1 . A global fit of 14 276 rovibrational transitions from the three bands provided an accurate set of ground state spectroscopic constants as well as excited state parameters for each of the three vibrational modes. The ground state structure was determined to be that of the puckered conformer having the NH bond in an equatorial arrangement.

The [H,C,N] molecular system is a very important model system to many fields of chemical physics. The experimental characterization of highly excited vibrational states of this molecular system with a stable HCN and a metastable HNC isomer is of special interest. The emission spectrum of the HNC isomer has been recorded at 1463 K using hot gas molecular emission (HOTGAME) spectroscopy in the wavenumber region of 3400 – 3800 cm - 1 with a resolution of 0.01 cm - 1 . The dense emission spectrum was analyzed with the spectrum analysis software SyMath™ implemented in the Mathematica™ computer algebra system. This work reports the analysis of the 1 v 2 l 0 → 0 v 2 l 0 band series up to v 2 = 7 and of the 1 v 2 l 1 → 0 v 2 l 1 band series up to v 2 = 4 . 15 rovibronic substates of HNC including all l = 1 , 3 , 5 , 7 sublevels of the v 1 v 2 l v 3 = 17 l 0 highly excited bending combination mode have been characterized for the first time and for the 14 known vibrational sublevels it was possible to improve the existing spectroscopic constants substantially. 23 vibrational sublevels are located for the first time relative to the 00 0 0 state. The exact position of these vibrational levels is an important contribution of this work to the spectroscopic characterization of the bending states of the [H,C,N] molecular system around the HNC minimum of the potential surface.

The rotational spectra of the protonated molecules NNOH+ and DCS+, and the ion complexes Ar ⋯ D 3 + , Ar ⋯ DCO+, and Ar ⋯ HNN+ have been detected by Fourier transform microwave spectroscopy at high spectral resolution, in which the supersonic molecular beam expands along the axis of the Farby–Perot cavity. These new measurements either better resolve or reveal additional line structure not observed in the previous lower resolution studies. Precise nitrogen or deuterium quadrupole coupling constants have been determined for the first time for both ions and Ar ⋯ DCO+; a tunneling splitting of 72 ± 5 kHz has been measured for the 1 0 , 1 → 0 0 , 0 transition of Ar ⋯ D 3 + .

The 1–0, 6–0 and 6–1 bands of the A 2 Π i → X 2 Σ + system of 13C16O+ and the 2–0 and 2–1 bands of the A 2 Π i → X 2 Σ + system of 14C16O+ have been recorded at high resolution for the first time. The 0–2 and 5–0 bands of the A → X system of 12C16O+ have also been recorded at higher resolution than in previous work. The spectra were excited in an air-cooled hollow cathode discharge and photographed using a 2-m plane grating spectrograph. The spectral resolution and the Doppler-broadened line widths are both ∼0.12 cm−1, and the experimental measurement precision of resolved lines is ∼0.02 cm−1. The measured line positions, sometimes in combination with literature data on the B 2 Σ + → A 2 Π i transition, have been employed in deperturbation analyses of level crossings in the near-degenerate A(0)∼X(10) and A(5)∼X(14) interactions in 12C16O+, the A(1)∼X(11) and A(6)∼X(15) interactions in 13C16O+, and the A(2)∼X(12) interaction in 14C16O+. No radial dependence of the electronic perturbation matrix elements HSO(r) and HRE(r) could be detected over the narrow range of r-centroids (1.477–1.501 A), and the mean values of these parameters are HSO = −49.06(15) cm−1 and HRE = 0.211(2). Using iteratively improved RKR potentials and FC-overlap integrals, the mean HSO and HRE were employed in least-squares analyses of A → X literature data involving A(υ) levels of the three isotopologues that are affected by interactions with one or two distant X(υ∗) levels. The fitted parameters of the A 2 Π i state (Bυ, Aυ, ADυ, pυ, qυ) exhibit υ-dependences that are much smoother than those employing perturbed parameters determined in previous investigations. In addition, a significant electronic isotope effect has been characterized. The separations Te(A)–Te(X) of the minima of the A and X states of 13C16O+ and 14C16O+ are less than that of 12C16O+ by 0.39 and 0.73 cm−1, respectively. Although Born–Oppenheimer breakdown of this magnitude is surprising, it is similar to that found for the B 2 Σ + state of CO+.

Fourier transform spectra of mono-13C ethylene have been recorded in the 8.4–14.3-μm spectral region (700–1190 cm−1) using a Bruker 120 HR interferometer at a resolution of 0.0017 cm−1 allowing the extensive study of the set of resonating states {101, 81, 71, 41, 61}. Due to the high resolution available as well as the extended spectral range involved in this study, a much larger set of line assignments are now available. The present analysis has lead to the determination of more accurate spectroscopic constants, including interaction constants, than were obtained in earlier studies. In particular, the following band centers were derived: ν0(ν10) = 825.40602(30) cm−1, ν0(ν8) = 932.19572(15) cm−1, ν0(ν7) = 937.44452(10) cm−1, ν0(ν4) = 1025.6976(14) cm−1. Finally a synthetic spectrum was generated leading to the assignment of a number of 13C12CH4 lines observed in an earlier heterodyne spectroscopic study.

The Fourier-transform absorption spectrum of 15 N 2 16 O -enriched nitrous oxide has been recorded at the Doppler limited resolution in the spectral range 3500–9000 cm−1. 6523 Transitions of 15 N 2 16 O were observed and assigned based on the global effective Hamiltonian model. The band-by-band analysis led to the determination of the ro-vibrational parameters of a total of 65 bands. Among these bands, 39 are newly observed, and the rotational analysis of 26 others were significantly extended and improved.

Laser-induced fluorescence experiments, using Rh metal and silane and jet-cooling, reveal a rich band spectrum of RhSi in the UV–visible region between 420 and 520 nm.This represents the first such observation for this free radical. The molecular ground state is identified as a 2 Σ + state derived principally from a σ 2 π 4 δ 4 σ 1 configuration and the electronic transition arises from promotion of the unpaired σ electron, localized on the Rh atom, to a ligand-sensitive π-orbital which is anti-bonding. A (0,0) band of the [22.6] 2 Σ + –X 2 Σ + system has been recorded near 442.55 nm at 200 MHz resolution. The band is red-degraded and all the rotational structure is resolved and a small hyperfine splitting has been measured. The (0,0) sub-bands of the [20.2] 2 Π–X 2 Σ + system lie near 495 nm. All bands of the system are strongly red-degraded. The (2,0) sub-bands have been recorded at 200 MHz resolution; all the rotational structure is resolved and a small hyperfine splitting measured, however, the upper states have proven to be perturbed. Dispersed fluorescence from numerous bands has been examined. Analysis of all the data provides the following molecular parameters for the X 2 Σ + state (in cm −1 ): B 0 = 0. 183695, D 0 = 3.76 × 10 −8 , γ 0 = −0.05083, γ 0D = 1.08 × 10 −5 , and ω e = 522. The measured bond length is 0.2043 nm. A simple molecular orbital scheme accounts for the observations.

The Fourier-transform absorption spectrum of 15N14N16O-enriched nitrous oxide has been recorded at the Doppler limited resolution in the spectral range 3500–9000 cm−1. More than 15 000 transitions of 15N14N16O were observed and assigned based on the global effective Hamiltonian model. The band-by-band analysis led to the determination of the ro-vibrational parameters of a total of 133 bands. Among these bands, 103 were newly observed, and the rotational analysis of 30 others were significantly extended and improved.

The Fourier transform gas-phase infrared spectrum of pyrrole, C4H5N, has been recorded with a resolution of ca. 0.003 cm−1 in the 900–1500 cm−1 spectral region. Four fundamental bands, ν8(A1; 1016.9 cm−1), ν23(B2; 1049.1 cm−1), ν7(A1; 1074.6 cm−1), ν20(B2; 1424.4 cm−1) and the overtone band 2ν16(A1; 962.7 cm−1) have been analysed using the Watson model. The ν8 and 2ν16 bands are unperturbed; the ν7 and ν23 bands are locally perturbed, while the ν20 band is globally perturbed by weak c-Coriolis resonance. Upper state vibrational term values, and rotational and centrifugal distortion constants, have been obtained from fits using S-reduction and Ir-representation as well as A-reduction and IIIr-representation. A set of ground state rotational and centrifugal distortion constants using A-reduction was obtained from a simultaneous fit of ground state combination differences from all five bands and previous microwave and millimetre-wave data.

Line positions and strengths of 16O13C16O (636), 16O13C18O (638) and 16O13C17O (637), and 18O13C18O (838) bands were measured using natural and 13C- and 18O-enriched samples of CO2 at room temperature. Twenty-five near infrared (NIR) absorption spectra were recorded at 0.01–0.013 cm−1 resolution with the McMath–Pierce Fourier transform spectrometer located at the National Solar Observatory on Kitt Peak, Arizona. Absorption cells with optical path lengths ranging from 0.347 m to 385 m were used with pressures ranging between 0.5 and 147 torr. Line strengths were obtained for 17 bands of (636) between 4697 and 6797 cm−1, 13 bands of (638) between 2192 and 4954 cm−1, 4 bands of (637) between 3437 and 4981 cm−1 and 7 bands of (838) between 2182 and 4888 cm−1. Band strengths and Herman–Wallis-like F-factor coefficients were determined from least-squares fits to over 2000 measured transition intensities involving 41 different bands. The observed line positions of several bands were analyzed to obtain the upper state term values and rotational constants. Five of the 18O13C18O bands and two of the 16O13C18O bands were modeled for the first time.

High-resolution Fourier transform infrared (HR-FTIR) spectra of R152a (CH 3 CHF 2 ) at room temperature were recorded at an unapodized resolution of 0.0019 cm −1 , and the fundamental bands ν 9 (868.7 cm −1 ) and ν 16 (941.7 cm −1 ) analysed. Transitions were assigned with the aid of Loomis–Wood plots and data fitted with Pickett’s SPFIT. The a -type ν 9 band is essentially unaffected by resonances, whilst the b -type ν 16 band shows distinct avoided crossings affecting a number of levels. These perturbations have been treated by explicit inclusion of interacting “dark” states with suitable Coriolis parameters in the fit of ν 16 transitions. Rotational levels of υ 16 = 1 in the vicinity of K c = 17 are perturbed via an a -axis Coriolis resonance with a state originating at 937.9 cm −1 , identified as υ 11 = 2. The levels around K c = 47 are perturbed by a b -axis Coriolis resonance with the combination state υ 10 = 1; υ 17 = 1 at 951.6 cm −1 .