Global fit of the high-resolution infrared spectrum of D2S

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 J^max = 25) with accuracies close to the experimental uncertainties.     

Use of Euler series to fit spectra with application to water

Power series expansions of water eigenstate energies in J and K converge poorly and show alternating signs of the coefficients of the power series. Euler series can be used effectively to change an alternating series into one where all the coefficients have the same sign and where the radius of convergence is increased. This paper extends the Euler series to a two-dimensional series in K² and [J (J + 1) − K²]. Application of this Euler series to the rotational energies of the ground state and the first 4 excited vibrational states of water allows a fit to experimental accuracy to J = 22 and K = 22. This fit has good convergence and also has predictive capability. It is much easier to fit the perturbed states because the Euler series allows the zero-order energy the perturbed states to be predicted with more confidence.     

Microwave spectroscopy of OCS in highly excited vibrational states through energy transfer from N2

The efficient vibrational energy transfer between the first excited vibrational state of N₂ and the asymmetric stretching vibrational state of OCS has allowed the observation of many pure rotational lines in different vibrational states of OCS up to 4101 cm^?1: (00⁰1), (01¹1), (02^l1), (10⁰1), (00⁰2), (21¹0), (03^l0), (04^l0), and (05^l0). Accurate values of some rotational, centrifugal distortion and l-doubling constants are determined.     

Laser Stark measurements on OCS including the observation of zero-field-forbidden ΔJ = 0, ±2 transitions

Laser Stark measurements have been made on the 02⁰000⁰0 and 03¹001¹0 vibrational transitions of ¹⁶O¹²C³²S, ¹⁶O¹²C³⁴S, and ¹⁸O¹²C³²S, and on the 03¹001¹0 transition of ¹⁶O¹³C³²S, using a CO₂ laser. In addition to providing dipole moment information for excited vibrational states, these measurements give vibrational band centers accurate to several megahertz. To aid in optical pumping experiments, several near coincidences between CO₂ laser transitions and OCS absorption lines are discussed. Electric-field-allowed ΔJ = 0 transitions are observed for the 2ν₂ band of ¹⁶O¹²C³²S and ¹⁶O¹²C³⁴S, as well as ΔJ = 2 transitions for the same band of ¹⁸O¹²C³²S.     

Laser Stark spectroscopy of OCS in the 9.5 μm region

Laser Stark spectra of carbonyl sulfide have been measured with parallel and perpendicular polarization of a 9.4 μm band CO₂ laser with the Stark field up to 90 kV/cm. Components of the P(2) and R(1) transitions of the 03¹0–01¹0 band and those of the P(1) transition of the 04⁰0–02⁰0 band for ¹⁶O¹²C³²S have been analyzed. Band origins, 1052.9446 (4) cm^?1 for 03¹0–01¹0 and 1057.7860 (5) cm^?1 for 04⁰0–02⁰0, and dipole moments, 0.7035 (16) D for 01¹0 and 0.6810 (24) D for 03¹P, are obtained.     

An analysis of the rotational, fine and hyperfine effects in the (0, 0) band of the AΠ-XΣ transition of manganese monohydride, MnH

High-resolution (±0.003 cm⁻¹), laser induced fluorescence (LIF) spectra of a supersonic molecular beam sample of manganese monohydride, MnH, have been recorded in the 17500-17800 cm⁻¹ region of the (0, 0) band of the A⁷Π-X⁷Σ ⁺ system. The low-N branch features were modeled successfully by inclusion of the magnetic hyperfine mixings of spin components within a given low-N rotational level using a traditional ‘effective’ Hamiltonian approach. An improved set of spectroscopic constants has been extracted and compared with those from previous analyses. The optimum optical features for future optical Stark and Zeeman measurements are identified.     

External cavity tunable diode laser spectra of the ν1 + 2ν4 stretch-bend combination bands of NH3 and NH3

The ammonia ν₁ + 2ν₄ perpendicular stretch-bend combination band has been investigated in spectra of ¹⁴NH₃ and ¹⁵NH₃ recorded in the 6400-6800 cm⁻¹ region with an external cavity tunable diode laser (ECTDL) spectrometer. For ¹⁴NH₃, new assignments were determined initially by extrapolating from published low-J jet-cooled beam results up to transitions of higher J and K. Corresponding ν₁ + 2ν₄ transitions for the ¹⁵NH₃ species were then found by identifying similar patterns of lines with a characteristic downshift of approximately 9.7 cm⁻¹. Assignments were confirmed employing ground-state combination differences. Term values, a-s inversion splittings, l-doubling energies and parameter estimates from simple single-state fits are reported for the two ammonia species.     

Mid-infrared diode laser spectroscopy of SO

The absorption spectrum of the fundamental band of SO⁺ (X²Π) has been recorded using a mid-infrared tunable diode laser spectrometer with the velocity modulation technique in an AC glow discharge of He/SO₂. Forty-two lines of SO⁺ were identified in the spectral range of 1230-1330 cm⁻¹. The observed rovibrational transitions together with the microwave data published previously were fitted to a standard effective Hamiltonian for ²Π states. Molecular constants for the ground and υ = 1 vibrational states were derived. The band origin was determined to be 1291.5299(27) cm⁻¹.     

High-resolution spectroscopy of the ν8 band of methylene bromide using a quantum cascade laser

A continuous wave cavity ringdown spectrometer with a Fabry-Perot quantum cascade laser has been used to collect a rotationally-resolved infrared spectrum of the ν₈ vibrational band of methylene bromide in a slit nozzle expansion. In our laboratory, previous observations of the vibrational band were limited by spectral coverage to only the P and Q-branches and by the 24 MHz step-size of the laser [1]. The issue of limited spectral coverage has been resolved using a Fresnel rhomb and a wire grid polarizer to protect the laser from the destabilizing effects of back-reflection from the ringdown cavity. The frequency step-size of the spectrometer has been reduced from 24 MHz to 2 MHz. With both of these instrument enhancements, we have been able to record the R-branch of the vibrational band, and can resolve many lines that were previously blended in spectra acquired using a pinhole expansion nozzle. Significant hyperfine splitting was observed for the low-J transitions in the P and R-branches. It was possible to neglect the effects of hyperfine splitting for transitions involving J″ > 2 in the spectral assignment, and simulations using the constants obtained by fitting to Watson’s S-reduced Hamiltonian for CH₂⁷⁹Br⁸¹Br, and the A-reduced form for CH₂⁷⁹Br₂ and CH₂⁸¹Br₂, provide a good match to experimental spectra. A total of 297 transitions have been assigned for all three isotopologues, with a standard deviation of 0.00024 cm⁻¹(∼7 MHz).     

Analysis of the first triad of interacting states (0 2 0), (1 0 0), and (0 0 1) of D2O from hot emission spectra

The far-infrared and middle-infrared emission spectra of deuterated water vapour were measured at temperatures 1370, 1520, and 1940 K in the ranges 320-860 and 1750-3400 cm⁻¹. The measurements were performed in an alumina cell with an effective length of hot gas of about 50 cm. More than 3550 new measured lines for the D₂¹⁶O molecule corresponding to transitions from highly excited rotational levels of the (0 2 0), (1 0 0), and (0 0 1) vibrational states are reported. These new lines correspond to rotational states with higher values of the rotational quantum numbers compared to previously published determinations: J_max = 29 and K_a(max) = 22 for the (0 2 0) state, J_max = 29 and K_a(max) = 25 for the (1 0 0) state, and J_max = 30 and K_a(max) = 23 for the (0 0 1) state. The extended set of 1987 experimental rotational energy levels for the (0 2 0), (1 0 0), and (0 0 1) vibration states including all previously available data has been determined. For the data reduction we used the generating function model. The root mean square (RMS) deviation between observed and calculated values is 0.004 cm⁻¹ for 1952 rovibrational levels of all three vibration states. A comparison of the observed energy levels with the best available values from the literature and with the global predictions from molecular electronic potential energy surfaces of water isotopic species [H. Partridge, D.W. Schwenke, J. Chem. Phys. 106 (1997) 4618] is discussed. The latter confirms a good consistency of mass-dependent DBOC corrections in the PS potential function with new experimental rovibrational data.     

FTMW spectroscopy of jet-cooled 9-cyanoanthracene

Rotational spectrum of jet-cooled 9-cyanoanthracene has been observed in the 4-8 GHz region with a Fourier-transform microwave spectrometer. The present observation of 25 low-J transitions with J^′′?11 has confirmed the previous results on the rotational constants of the ground state determined by rotational coherence spectroscopy [J. Phys. Chem. A. 105 (2001) 1131] and provided the values with significantly improved precision. An accurate set of hyperfine splitting constants is also reported for the ¹⁴N nuclear quadrupole coupling. The electric dipole moment was determined from Stark effect measurements on several split components: μ_b(=μ)=4.406(7) D.     

Joint ro-vibrational analysis of the HDS high resolution infrared data

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 J^max = 23) with accuracies comparable with the experimental uncertainties.     

A study of the AΠ-XΣ and BΣ-XΣ band systems of scandium monosulfide, ScS, using Fourier transform emission spectroscopy and laser excitation spectroscopy

Emission spectra of the A²Π_3/2-X²Σ⁺ (0, 1), (0, 0), and (1, 0) bands and the B²Σ⁺-X²Σ⁺ (0, 1), (0, 0), (1, 0), (2, 0), and (3, 1) bands of ScS have been recorded in the 10 000-13 500 cm⁻¹ region at a resolution of 0.05 cm⁻¹ using a Fourier transform (FT) spectrometer. The A²Π_r-X²Σ⁺ (1, 0) band as well as the B²Σ⁺-X²Σ⁺ (0, 0) and (1, 0) bands have been recorded at high resolution (±0.001 cm⁻¹) by laser excitation spectroscopy using a supersonic molecular beam source. The FT spectral features range up to N = 148, while those recorded with the laser cover the “low-N” regions. The lines recorded with the laser exhibit splittings due to the ⁴⁵Sc (I = 7/2) magnetic hyperfine interactions, which are large (∼6.65 GHz) in the X²Σ⁺ state and much smaller in the B²Σ⁺ and A²Π states. The energy levels were modeled using a traditional ‘effective’ Hamiltonian approach, and improved spectroscopic constants were extracted and compared with previous determinations and theoretical predictions.     

High resolution fourier transform spectrum of PD3 in the region of the stretching overtone bands 2ν1 and ν1+ν3

The infrared spectrum of the PD₃ molecule has been measured in the region of the first stretching overtone bands on a Fourier transform spectrometer with a resolution of 0.0068 cm⁻¹ and analyzed for the first time. More than 800 transitions with J^max=15 have been assigned to the bands 2ν₁ and ν₁+ν₃. An effective Hamiltonian was used which takes into account both the presence of resonance interactions between the states (2 0 0 0) and (1 0 1 0), and interactions of these with the third stretching vibrational state of the v=2 polyad, (0 0 2 0). A set of 44 spectroscopic parameters is obtained from the fit. This reproduces the 305 initial “experimental” upper rovibrational energies with an rms=0.0015 cm⁻¹.     

Rotational levels of the (0 0 0) and (0 1 0) states of D2O from hot emission spectra in the 320-860 cm region

The far-infrared emission spectra of deuterated water vapour were measured at different temperatures (1370, 1520, and 1950 K) in the range 320-860 cm⁻¹ at a resolution of 0.0055 cm⁻¹. The measurements were performed in an alumina cell with an effective length of hot gas of about 50 cm. More than 1150 new measured lines for the D₂¹⁶O molecule corresponding to transitions between highly excited rotational levels of the (0 0 0) and (0 1 0) vibrational states are reported. These new lines correspond to rotational states with higher values of the rotational quantum numbers compared to previously published determinations: J_max=26 and for the (0 0 0) ← (0 0 0) band, J_max=25 and for the (0 1 0) ← (0 1 0) band, and J_max=26 and for the (0 1 0) ← (0 0 0) band. The estimated accuracy of the measured line positions is 0.0005 cm⁻¹. To our knowledge no experimentally measured rotational transitions for D₂¹⁶O within an excited vibrational state have been available in the literature so far. An extended set of experimental rotational energy levels for (0 0 0) and (0 1 0) vibration states including all previously available data has been determined. For the data reduction we used the generating function model. The root mean square (RMS) deviation between observed and calculated values is 0.0012 cm⁻¹ for 692 rotational levels of the (0 0 0) state and 0.0010 cm⁻¹ for 639 rotational levels of the (0 1 0) vibrational state. A comparison of the observed energy levels with the best available values from the literature and with the global predictions from molecular electronic potential energy surface [J. Chem. Phys. 106 (1997) 4618] for the (0 0 0) and (0 1 0) states is discussed.     

HDO absorption spectrum above 11 500 cm: Assignment and dynamics

Assignment of an HDO line list extracted from a recently measured H₂O/HDO/D₂O Fourier transform absorption spectrum recorded in the 11 600-23 000 cm⁻¹ region by Bach et al. (M. Bach, S. Fally, P.-F. Coheur, M. Carleer, A. Jenouvrier, A.C. Vandaele, J. Mol. Spectrosc. 232 (2005) 341-350.) is presented. More than 94% of the 3256 lines are given quantum number assignments and ascribed to line absorption by HDO; most of the remaining lines are actually due to D₂O. High accuracy variational predictions of line positions and intensities are used for the spectral assignment process. Assignments to the ν₁ + 5ν₃, 2ν₂ + 5ν₃, ν₁ + ν₂ + 3ν₃ and ν₁ + 6ν₃ bands are presented for the first time. Comparisons are made with published ICLAS spectra covering the same spectral region and suggestions made for its recalibration. The results are used to illustrate the dynamical behaviour of highly excited vibrational states of HDO and to discuss previous vibrational assignments to high lying rotation-vibration states of this system.     

Lifetimes and transition frequencies of several singlet ungerade states in N2 between 106 000 and 109 000 cm

Using a narrow-band tunable XUV source, ultra-high resolution 1 XUV + 1 UV two-photon ionisation spectra were recorded of transitions to several singlet ungerade states in ¹⁴N₂ and ¹⁵N₂ in the range 106 000-109 000 cm⁻¹. The natural linewidths of the individual rotational spectral lines were determined and the resulting lifetimes were found to depend on vibrational level and for the c₃¹Π_u (v = 1) level also on isotope. Furthermore, accurate transition frequencies were determined and for several bands, lines near bandhead regions were resolved for the first time.     

New high-resolution analysis of the {ν1 + ν3} band of the NO2 isotopomer of nitrogen dioxide: Line positions and intensities

The high-resolution Fourier transform absorption spectrum of an isotopic sample of nitrogen dioxide, ¹⁵N¹⁶O₂, was recorded in the 3.4 μm region. Starting from the results of a previous study [Y. Hamada, J. Mol. Struct. 242 (1991) 367-377] a new analysis of the ν₁ + ν₃ band located at 2858.7077 cm⁻¹ has been performed. This new assignment concerns (1 0 1) energy levels involving rotational quantum numbers up to K_a = 10 and N = 54. Using a theoretical model which accounts for both the electron spin-rotation resonances within each vibrational state and the Coriolis interactions between the (1 2 0) and (1 0 1) vibrational states, the spin-rotation energy levels of the (1 0 1) vibrational state could be reproduced within their experimental uncertainty. In this way, the precise vibrational energy, rotational, spin-rotation, and coupling constants were achieved for the {(1 2 0), (1 0 1)} interacting states of ¹⁵N¹⁶O₂. Using these parameters and the transition moment operator which was obtained for the main isotopic species, ¹⁴N¹⁶O₂, a comprehensive list of the line positions and intensities was generated for the ν₁ + ν₃ band of ¹⁵N¹⁶O₂.     

Three- and two-photon absorption in HCl and DCl: identification of Ω = 3 states and state interaction analysis

High resolution (3 + 1) and (2 + 1)REMPI spectra of HCl and DCl for total current detection at room temperature or TOF mass detection after jet cooling were recorded for the spectral region 89 000-89 600 cm⁻¹. Analysis of the (3 + 1)REMPI spectra by use of three-photon absorption modeling allowed, for the first time, identification and characterization of the l (³Φ₃) states. Consistent anomalies in spectral structures due to transitions to the j (³Σ⁻) (0⁺) state are interpreted as being due to interactions with the V (¹Σ⁺) ion-pair states. Interaction strengths are evaluated. Simulation analyses and determination of isotope shifts allowed evaluation of vibrational and rotational spectroscopic parameters for the l (³Φ₃) and the j (³Σ⁻) (0⁺) states for both molecules.     

High sensitivity ICLAS of H2O in the 12,580-13,550 cm transparency window

High-sensitivity Intracavity Laser Absorption Spectroscopy (ICLAS) is used to measure the high resolution absorption spectrum of H₂¹⁸O between 12,580 and 13,550 cm⁻¹. This spectral region covers the 3v+δ polyad of very weak absorption. Four isotopologues of water (H₂¹⁸O, H₂¹⁶O, H₂¹⁷O, HD¹⁸O) are found to contribute to the observed spectrum. Spectrum analysis is performed with the aid of variational calculations and allowed for assigning 1126 lines belonging to H₂¹⁸O, while only 160 H₂¹⁸O lines are included in the HITRAN-2008 database. Altogether, 823 accurate energy levels of H₂¹⁸O are determined from transitions attributed to 26 upper vibrational states, 438 of them being reported for the first time. New information includes energy levels of four newly observed vibrational states of H₂¹⁸O: (2 4 0), (1 4 1), (0 4 2) and (2 3 1) at 13,167.718, 13,212.678, 13,403.71 and 15,073.975 cm⁻¹, respectively. H₂¹⁸O transitions involving highly excited bending states like (1 6 0), (0 6 1), (0 7 1), (1 7 0), (0 9 0) and even (0 10 0) have been identified as a result of an intensity borrowing from stronger bands via high-order resonance interactions. Thirty-six new energy levels of H₂¹⁷O, present with a 2% relative concentration in our sample, could be determined. The rotational structure of the (0 2 3) state of HD¹⁸O at 13,245.497 cm⁻¹ is also reported for the first time.