Highlights•First observation of the 6–0 band of CO.•Upper-level energies determined with an accuracy of 3×10−4 cm−1.•Line parameters of the 6–0 band of 12C16O are presented.The extremely weak 6–0 absorption band of the 12C16O molecule was recorded for the first time using a very sensitive cavity ring-down spectrometer. Frequencies of a few atomic transitions in the 0.8 μm region, transferred to the passive modes of a thermally stabilized Fabry-Pérot interferometer, are used to calibrate the observed spectra with an absolute accuracy of 3×10−4 cm−1. Line parameters, including line positions, intensities, self-broadening and -shifting coefficients were derived by fitting the observed spectra with the Voigt profile.

Long-lived radioactive krypton isotopes, 81Kr (t1/2 = 229 000 year) and 85Kr (t1/2 = 10.76 year), are ideal tracers. 81Kr is cosmogenic and can be used for dating groundwater beyond the 14C age. 85Kr is a fission product and can be applied in atmospheric studies, nuclear safety inspections, and dating young groundwater. It has long been a challenge to analyze radio-krypton in small samples, in which the total number of such isotopes can be as low as 1 × 105. This work presents a system developed to analyze 81Kr and 85Kr from a few liters of air samples. A separation system based on cryogenic distillation and gas chromatographic separation is used to extract krypton gas with an efficiency of over 90% from air samples of 1–50 L. 85Kr/Kr and 81Kr/Kr ratios in krypton gases are determined from single-atom counting using a laser-based atom trap. In order to test the performance of the system, we have analyzed various samples collected from ambient air and extracted from groundwater, with a minimum size of 1 L. The system can be applied to analyze 81Kr and 85Kr in environmental samples including air, groundwater, and ices.

H216O lines in the spectral range of 12,573–12,753 cm−1 have been recorded by cavity ring-down spectroscopy. Low-pressure water vapor (0.25 Torr) was used to limit the pressure-induced line shift. The absolute line positions were calibrated with Rb atomic transitions and a thermo-stabilized Fabry–Pérot interferometer. Positions of 73 lines with intensities larger than 1×10−25cm−1/(moleculecms−2) have been determined. For well-isolated lines, the absolute frequency accuracy is estimated to be 3×10−5cm−1, which is also confirmed by the ground-state combination differences. Comparison between the line positions obtained in this work and those from HITRAN shows a systematic deviation of 0.001cm−1.Highlights► Cavity ring-down spectra of H2O lines in the 784–795 nm region were measured. ► Absolute positions of 73 water lines were determined with 3E−5 cm−1 accuracy. ► HITRAN H2O line positions in this region have a systematic shift of 0.001 cm−1.

Complicated high-resolution spectral structures are often observed for molecules doped in solid molecular hydrogen. The structures can result from miscellaneous effects and are often interpreted differently in references. The spectrum of the ν3 band of CO2 in solid para-H2 presents a model system which exhibits rich spectral structures. With the help of the potential energy simulation of the CO2 molecule doped in para-hydrogen matrix, and extensive experiments with different CO2 isotopologues and different ortho-hydrogen concentrations in the matrix, the spectral features observed in p-H2 matrix are assigned to the CO2···(o-H2)n clusters and also to energy level splitting that is due to different alignments of the doped CO2 molecules in the matrix. The assignments are further supported by the dynamics analysis and also by the spectrum recorded with sample codoped with O2 which serves as catalyst transferring o-H2 to p-H2 in the matrix at 4 K temperature. The observed spectral features of CO2/pH2 can potentially be used as an alternative readout of the temperature and orthohydrogen concentration in the solid para-hydrogen.

The spectroscopy of molecules trapped in para-hydrogen (p-H2) matrix revealed unique properties of the quantum solid environment. But it has been limited to the low-lying vibrational states while we believe the investigations on the highly excited states may provide new viewpoint of such interesting system. Here we report the infrared spectroscopy of nitrous oxide in solid para-hydrogen in the 1000–7000 cm−1 region. Fourteen bands including very high overtones like 5ν15ν1 were assigned for each of the three isotopologues of N2O: N142O16, N14N15O16, and N15N14O16. All these observed N2O/p-H2 bands are found red-shifted. The relative intensity of the 5ν15ν1 band in solid hydrogen matrix was found to be about 100 times higher than that in the gas phase which implies anomalous enhancement by the matrix environment. We also observed “anomalous” high-resolution structures in the ν3ν3, ν1+ν3ν1+ν3 and 2ν32ν3 bands of N2O/p-H2. The multiple peaks in the subtle band structures were found regularly separated, temperature-dependent and reversible. The simulation reveals a 142 cm−1 high barrier between different orientations of the N2O molecule in the p-H2 matrix. The barrier can be accounted for by the hours-long relaxation revealed from the spectra observed at 4.3 K. According to the characters of the observed spectral features, we conclude that the multiple peaks may originate from the multiple orientations of the N2O molecules isolated in the p-H2 matrices. It can also interpret that why some bands are with spreading structures while others are just significantly broadened.

The solid neon matrix isolated spectrum of CO2 are recorded in the 2–5 μm region. Natural and 13C or 18O enriched CO2 samples were used and the nν1 + ν3 (n = 0, 1, 2) series bands of different CO2 isotopologues have been observed. The solid neon matrix shift due to Fermi-resonance of bands within the same vibrational polyad is analyzed.

The absorption spectrum of 14N15N16O-enriched sample of nitrous oxide has been recorded at Doppler limited resolution with a Fourier-transform spectrometer in the spectral range 3500–9000 cm−1. More than 12 000 transitions of 14N15N16O were observed and ro-vibrationally assigned on the basis of the global effective Hamiltonian model. The band-by-band analysis led to the determination of the ro-vibrational parameters of a total of 107 bands. Among the 107 bands, 80 are newly observed, for 27 others the rotational analysis is significantly extended and improved. The effective Hamiltonian parameters are determined from global fitting to the observed line positions presented in this paper and collected from the literature. As a result, a set of 117 obtained effective Hamiltonian parameters reproduces 16 134 observed line positions of 148 bands with RMS of 0.0014 cm−1.

The absorption spectrum of the 18O enriched carbon dioxide has been recorded at Doppler limited resolution with a Fourier transform spectrometer in the spectral range 3800–8500 cm−1. Seventeen cold bands (14Σ–Σ and 3Σ–Π) and nine hot bands (9Π–Π) of 12C18O2, nineteen cold bands (18Σ–Σ and 1Σ–Π) and eighteen hot bands (6Σ–Σ, 9Π–Π and 3Δ–Δ) of 16O12C18O have been observed. Among them, 14 12C18O2 bands and 12 16O12C18O bands are observed for the first time. The spectroscopic parameters Gv, Bv, and centrifugal distortion constants, have been determined for all observed bands. Effective Hamiltonian parameters for the 12C18O2 isotopic species are retrieved from the global fitting of the observed line positions presented in this paper and collected from the literature. As the result, 65 obtained effective Hamiltonian parameters reproduce 5443 observed line positions of 73 12C18O2 bands with RMS = 0.00145 cm−1.

Apparatus integrating a Fourier transform-infrared (FT-IR) spectrometer and a mid-infrared difference frequency generation (DFG) laser spectrometer was built for the study of the matrix isolation spectrum in solid molecular hydrogen. A 3-cm-long molecular hydrogen crystal was grown in a liquid-helium Dewar, and its infrared absorption spectrum in the 1-5 μm region was recorded to test the system. The W0(0) (ν=0←0, J=6←0) line around 2410 cm−1 of solid hydrogen was investigated with the DFG laser spectroscopy. High-resolution matrix isolation spectrum of CO2 co-deposited with hydrogen on a BaF2 cold plate at liquid-helium temperature was studied.

Fourier transform spectra of water vapor enriched in 18O and 17O were recorded between 8012 and 9336 cm−1 and analyzed for the first time. High accuracy ab initio predictions of line positions and intensities by Partridge and Schwenke [J. Chem. Phys. 106 (1997) 4618–4639; 113 (2000) 6592–6597] were used in the process of spectrum assignment. Transitions involving the (031), (111), (130), (210), and (012) upper vibrational states were identified in the recorded spectra. As a result, 514 and 244 precise ro-vibrational energy levels were derived for the H218O and H217O molecules, respectively. High-order resonance perturbations between levels of the vibrational states involved were evidenced leading to the identification of a number of rotational levels of the (050) and (060) highly excited bending states.

High resolution Fourier transform spectra of the HDS molecule were recorded and analyzed for the first time in the region of the bands ν1 + 2ν2 (3938.6 cm−1), ν1 + ν3 (4522.6 cm−1), 2ν2 + ν3 (4638.8 cm−1), 2ν1 + ν2 (4767.7 cm−1), ν1 + ν2 + ν3 (5525.2 cm−1), 3ν1 (5560.6 cm−1), ν1 + 2ν3 (7047.2 cm−1), and 2ν2 + 2ν3 (7123.9 cm−1). The ro-vibrational energies of the upper vibrational states of these bands together with the ro-vibrational energies of 12 other bands already studied at high resolution were used as inputs in a Global Fit analysis firstly described in [O.N. Ulenikov, G.A. Onopenko, H. Lin, J.-H. Zhang, Z.-Y. Zhou, Q.-S. Zhu, R.N. Tolchenov, J. Mol. Spectrosc. 189 (1998) 29–39]. In this case, the resonance interactions between the states (v1v2v3) and (v1 ± 2 v2 ∓ 1 v3 ∓ 1) were taken into account. The resulting set of 143 parameters reproduces all the experimental data (2984 vibration–rotation energies of 20 vibrational states which correspond to about 9700 ro-vibrational transitions with Jmax = 23) with accuracies comparable with the experimental uncertainties.

The absorption spectrum of the natural sample of nitrous oxide has been recorded at Doppler limited resolution with a Fourier-transform spectrometer in the spectral range 5000–10 000 cm−1. Ten cold bands (8Σ − Σ and 2Σ − Π), thirteen hot bands (11Π − Π, Σ − Σ, and Δ − Δ) of 14N216O and the 3ν3 band of 14N15N16O have been newly detected. The uncertainty of the line position determination is estimated to be about 0.005 cm−1 for unblended lines. The assignment of the spectrum has been done with the help of the prediction performed within the framework of the polyad model of effective Hamiltonian. The spectroscopic parameters Gv, Bv, Dv, Hv, and qv have been determined for all newly detected bands. The line intensities of 13 weak bands have been measured. The uncertainty of the obtained line intensity values varies from 7 to 13%.

High-resolution Fourier-transform spectra of the D2S molecule in the regions of polyads of interacting vibrational states v = 3/2, 2, 5/2, 3 and 7/2 (v = v1 + v2/2 + v3) were recorded for the first time with a Bruker IFS 120 Fourier-transform interferometer and analysed. A global fit of all currently available rotation–vibration energies has been made for 22 vibrational states of the D2S molecule. The resulting set of 231 parameters reproduces all the initial experimental data (about 3670 vibration–rotation energies which correspond to more than 9700 ro-vibrational transitions with Jmax = 25) with accuracies close to the experimental uncertainties.

The high-resolution absorption spectrum of the HDO molecule was recorded with a Fourier-transform interferometer in the region of 8900–9600 cm−1, where the strongly interacted bands 2ν1 + ν3, 3ν1 + ν2, ν1 + 2ν2 + ν3, 2ν1 + 3ν2, 4ν2 + ν3, ν1 + 5ν2, and 7ν2 are located. About 1000 transitions were assigned to these seven bands based on the ab initio predictions [J. Chem. Phys. 106 (1997) 4618]. Altogether, 375 upper energy levels were determined, including 24 energy levels of the highly excited bending (070) state. On that basis, the necessity of the “Effective Hamiltonian” concept in the spectroscopic analysis is discussed.

High-resolution Fourier transform spectrum of the HD32S molecule was studied in the region of 5000–9000 cm−1. More than 1600 observed transitions yielded 239, 264, 131, and 116 upper state ro-vibrational energies of the states (002), (012), (003), and (013), respectively. With a Watson-type effective Hamiltonian model, the ro-vibrational parameters of these four upper states were determined by a least-square fitting which can reproduce the ro-vibrational energies close to the experimental accuracy. The relative linestrengths are also discussed.

High-resolution Fourier transform infrared spectrum of H232S was recorded and analyzed in the region of the second hexade v=v1+12v2+v3=2.5. More than 1700 transitions were assigned to the 2ν1 + ν2, ν1 + ν2 + ν3, ν1 + 3ν2, 3ν2 + ν3, 5ν2, and ν2 + 2ν3 bands with the maximum value of quantum number J equal to 18, 18, 13, 11, 13, and 9, respectively. The theoretical analysis was fulfilled with a Hamiltonian model which takes into account numerous resonance interactions between all the vibrational states in this polyad. By a least-square fitting, finally 505 upper energy levels were reproduced by 80 parameters with an rms deviation of 0.0019 cm−1.

The absolute line intensities of the Fermi triad 2003i–00001 (i = 1, 2, 3) of 12C16O2 and 13C16O2 isotopic species of carbon dioxide were retrieved from Fourier-transform spectra recorded at Doppler limited resolution in the region 9200–9700 cm−1. The accuracy of the line intensity determination is estimated to be better than 15% for most lines. The vibrational transition dipole moments squared and Herman–Wallis coefficients have been determined. The global fittings of the observed line intensities within the framework of the effective operators method have been performed. The fitting results reproduce the data within experimental uncertainty.

The absolute line intensities of 13C16O2 were retrieved from Fourier-transform spectra recorded in the region 4200–8500 cm−1. The accuracy of the line intensity determination is estimated to be 5% or better for most lines and about 10% for weak ones. The vibrational transition dipole moments squared and Herman–Wallis coefficients have been determined. The global fittings of the observed line intensities within the framework of the effective operators approach have been performed. As the result of the fittings, most line intensities are reproduced within the experimental accuracy. The comparison between the new measured data and the HITRAN database are also carried out.

High-resolution Fourier transform infrared spectrum of H2S was recorded and analyzed in the region of the v=v1+12v2+v3=3.5 polyad. More than 450 transitions were assigned to the 3ν1 + ν2 and 2ν1 + ν2 + ν3 bands with the maximum values of quantum numbers J and Ka equal to 14, 7, and 14, 9 for these two bands, respectively. The theoretical analysis was fulfilled with the Hamiltonian which takes into account strong resonance interactions among the studied vibrational states (3 1 0), (2 1 1), and also “dark” states (0 3 2) and (2 3 0). The rms deviation is 0.0019 cm−1. The intensity borrowing effect in the doublets in the P-branch transitions of the 3ν1 + ν2 and 2ν1 + ν2 + ν3 bands is observed and discussed.

The HDO absorption FT spectrum is recorded and analyzed in the 7500–8200 cm−1 spectral region. The high accuracy ab initio calculation of Schwenke and Partridge was successfully applied for spectrum assignment that resulted in derivation of 508 precise rovibrational energy levels for the (3 0 0), (0 3 1), (1 1 1), (0 6 0), (2 2 0), and (0 0 2) states, with 295 of them being reported for the first time. In particular, eight new energy levels, including the band center at 7914.3170 cm−1, were derived for the highly excited bending (0 6 0) state from transitions borrowing their intensities through local high-order resonance coupling with the (3 0 0) and (0 3 1) states.

High-resolution Fourier transform infrared spectrum of H2S was recorded and analyzed in the region of the v=v1+v2/2+v3=3 poliad. Experimental transitions were assigned to the 3ν1, 2ν1+ν3, ν1+2ν3, 3ν3, 2ν1+2ν2, and ν1+2ν2+ν3 bands with the maximum value of quantum number J equal to 11, 14, 10, 11, 8, and 11, respectively. The theoretical analysis was fulfilled with the Hamiltonian model which takes into account numerous resonance interactions between all the mentioned vibrational states. The rms deviation of the reproduction of 510 upper energy levels (derived from more than 1550 transitions) with 75 parameters was 0.0022 cm−1.

The absorption spectrum of a 13C enriched carbon dioxide sample has been recorded with a Fourier-transform spectrometer in the spectral range 4000–9500 cm−1. In addition to six bands observed from the spectrum of the atmosphere of Venus in this region, eight new 16O13C18O bands were measured. The new observations together with the data collected from the literature have been used to fit parameters of an effective Hamiltonian for the 16O13C18O. More than 4000 line positions in 38 bands have been used to derive 48 parameters of effective Hamiltonian. The RMS (root-mean-square of residuals) of the fit is 0.00106 cm−1.

The capabilities of intra-cavity laser absorption spectroscopy associated with a high-resolution Fourier-transform spectrometer (FT-ICLAS) are investigated with a Ti:Sapphire laser. Weak absorption lines of atmospheric water were used to test the accuracy of absolute intensity measurements by FT-ICLAS leading to an excellent agreement (a few %) with the HITRAN data. The performances in terms of spectral resolution (0.028 cm−1) and sensitivity () are illustrated by the spectroscopic study of the overtone spectrum of between 12 250 and 12 400  cm−1 which allowed for a significant improvement of recent cavity ring-down measurements. Among the three Π–Σ bands rotationally analyzed, one is newly observed. The absolute intensity values of the bands are given.