Line strengths,spin-splittings,and forbidden transitions in the (101) band of 14N16O2

Measurements of line strengths in the (101) and (111)-(010) bands of ¹⁴N¹⁶O₂ have been made at a resolution of 0.02 cm^?1 in the region 2863 to 2934 cm^?1. The strength data in the (101) band were analyzed to determine a vibrational band strength and coefficients of the F factor. Each subband for K_?1 ≤ 9 was analyzed separately and all the F-factor coefficients in terms of the rotational quantum number, N, were found to be too small to be of significance. However, F was found to be dependent on K_?1 and the experimentally determined subband strengths were least-squares fitted to the expression S_v⁰·F, where S_v⁰ = 68.3 cm^?2 atm^?1 at 296 K and F = 1 + (2.899 × 10^?3)K_?1 + (4.08 × 10^?3)K_?1² ? (2.34 × 10^?4)K_?1³. The integrated strengths for the (101) and (111)-(010) bands were found to be 70.9 ± 2.3 and 2.7 ± 0.3 cm^?2 atm^?1 at 296 K, respectively. Also included in this study are measurements of line center positions in the two bands and spin-splittings in the (101) band. Recent frequency measurements of lines with K_?1 ≤ 8 in the (101) band have been made at a resolution of 0.0033 cm^?1 by V. Dana and J. P. Maillard (J. Mol. Spectrosc.71, 1–4) (1978)) for the region above 2889 cm^?1 and our values are in excellent agreement with theirs. Separations of the split lines measured in this work (K_?1 ≤ 10) agree well with calculated values using expressions which include the η_aaaaK_?1⁴ term with η′_aaaa = ?1.70 ± 0.15 × 10^?4 cm^?1 as derived for the (101) state. Three forbidden (ΔN ≠ ΔJ, ΔK_?1 = 0) transitions in the (101) band were observed with their identifications based on the agreement between measured and calculated line positions and strengths.     

Laser-induced-fluorescence Fourier transform spectrometry of the XOg+ state of I2: Extensive analysis of the BOu+ → XOg+ fluorescence spectrum of 127I129I and 129I2

An extensive rotational analysis of the vibrational levels of the XO_g⁺ state of ¹²⁷I¹²⁹I (5 ≤ v″ ≤ 110) and ¹²⁹I₂ (4 ≤ v″ ≤ 108) has been done from laser-induced-fluorescence analyzed with a Fourier transform spectrometer. The usual Dunham relationships are checked. For the range explored the lines can be recalculated with an accuracy better than 0.010 cm⁻¹ and even 0.005 cm⁻¹ for low J values. Checks are done from absolute hyperfine measurements.     

Analysis of the ν6 band of carbonyl fluoride

The vibration-rotation spectrum of the ν₆ fundamental band of carbonyl fluoride (COF₂) has been recorded at room temperature and 0.005 cm⁻¹ resolution, using a Fourier transform spectrometer. Although the strong Q branch at 774 cm⁻¹ is only partially resolved in the spectrum, most of the K structure of various J subgroups in the P and R branches has been fully resolved. More than 1500 transitions belonging to J values up to 40 have been assigned and simultaneously fitted with the microwave frequencies reported by J. H. Carpenter [J. Mol. Spectrosc. 50, 182–201 (1974)] with a standard deviation of 0.0006 cm⁻¹. By incorporating quartic and sextic centrifugal distortion coefficients in Watson's reduced Hamiltonian in the I^r representation, upper state rotational constants A, B, and C have been determined to an accuracy better than 10⁻⁵ cm⁻¹. Ground state rotational and fourth order centrifugal distortion constants were constrained in the analysis to the values reported by W. Lewis-Bevan et al. [J. Mol. Spectrosc. 113, 458–471 (1985)].     

Analysis of the ν6 band of 12CH3D at 8.6 μm

The ν₆(E) fundamental vibration-rotation band of monodeuteromethane (¹²CH₃D) has been recorded in the spectral range 1033–1270 cm^?1 with a resolution of approximately 0.04 cm^?1. Of the 669 transitions with J′ ≤ 17 identified, 633 have been retained for the determination of the rotational levels in the upper state v₆ = 1. The Coriolis interaction between the v₆ = 1(E) and v₃ = 1 (A₁) vibrational states of ¹²CH₃D results in large A₁A₂ splittings of levels with v₆ = 1 and |K ? l₆| = 0 or 3; the mixing in K and l₆ also gives rise to some ten forbidden transitions observed in the spectra. These effects have been very well explained within the formulation based on the contact transformation method. Values of 15 molecular structure constants of the v₆ = 1 state have been determined from a least-squares analysis of the 633 retained transitions. These constants can be used to estimate values of the upper-state energies up to fourth order, and through them the spectral positions of the 633 retained transitions are reproduced with an overall standard deviation of 0.013 cm^?1, which is within experimental uncertainties.     

The A2Σ+-X2Πi electronic band system of the OD free radical: Spectroscopic data for the 0-0 sequence,and rotational term values for A2Σ+ and X2Πi

The A²Σ⁺-X²Π_i emission system of the OD radical has been recorded at high resolution from a discharge through flowing D₂O at 0.1 torr pressure. The 0-0, 1-1, and 2-2 bands of the Δv = 0 sequence have been analyzed in detail for the first time. A table of the vacuum wavenumbers and wavelengths in air of the rotational lines of these bands is presented, together with some additional measurements for the 0–1 band. The data are used to obtain a self-consistent set of term values for v′ and v″ = 0, 1, which reproduces the observed line frequencies with an average deviation of less than 0.02 cm^?1. Earlier, lower resolution data for bands with v′ and v″ = 2, 3 are also combined with the present measurements to give approximate term values for these higher levels.     

Quantitative laboratory spectra and spectral line parameters for the v2 and v4 bands of PH3 applicable to spectral radiative models of the atmosphere of Jupiter

Quantitative laboratory PH₃ absorption spectra were obtained in the 800–1350 cm^-1 region, at ～0.05 cm^-1 resolution, with gas amounts corresponding to observed PH₃ absorptions in the atmosphere of Jupiter. A compilation of spectral line positions, intensities and ground state energies has been generated for the v₂ and v₄ bands of PH₃. Line-by-line calculations have been compared with the experimental spectra.     

The ground state of molecular hydrogen

The v = 0?0 quadrupole spectrum of H₂ has been recorded using a 0.005-cm^?1 resolution Fourier transform spectrometer. The rotational lines S(1) through S(5) are observable in the spectra, in the region 587 to 1447 cm^?1. The spectral position for S(0) was also obtained from its v = 1-0 ground-state combination difference. The high accuracy of the H₂ measurements has permitted a determination of four rotational constants. These are (in cm^?1) B₀ = 59.33455(6); D₀ = 0.045682(4); H₀ = 4.854(12) × 10^?5; L₀ = ?5.41(12) × 10^?8. The hydrogen line positions will facilitate studies of structure and dynamics in astrophysical objects exhibiting infrared H₂ spectra. The absolute accuracy of frequency calibration over wide spectral ranges was verified using 10-μm CO₂ and 3.39-μm CH₄ laser frequencies. Standard frequencies for 5-μm CO were found to be high by 12 MHz (3.9 × 10^?4 cm^?1).     

A new study of the ν 2(A 1) infrared band of phosphorus trifluoride

The high-resolution Fourier transform infrared spectrum of phosphorus trifluoride (PF₃) has been reinvestigated in the v_2?=?1 vibrational excited state near 487?cm^?1 (at a resolution of 3?×?10^–3?cm^–1). Thanks to our new accurate rotational ground-state C ₀ value, 0.159970436(69)?cm^–1, and to recent pure rotational measurements, 318 new infrared transitions of the ν ₂ fundamental band have been assigned, extending the rotational quantum number values up to K _max?=?71 and J _max?=?72. A merge, for the first time, of 135 reported microwave data (K _max?=?42 and J _max?=?49) within the v_2?=?1 excited level and 2860 rovibrational transitions yielded improved constants of ν ₂. Parameters of this band have been obtained, up to sextic centrifugal distortion constants, by least-squares fits, σ _IR?=?3.60?×?10^–4?cm^–1 and σ _MW?=?5.53?×?10^–6?cm^–1 (166?kHz). Comparison of these constants with those measured previously by infrared spectroscopy reveals orders of magnitude higher accuracy of these new values.     

Far infrared spectrum and spectroscopic constants of AsH3 in the ground state

The far ir spectrum of arsine, AsH₃, was recorded in the range 25–100 cm^?1 with a resolution of approximately 0.004 cm^?1. ΔJ = +1, ΔK = 0 rotational transitions were measured and assigned up to J″ = 12. These transitions, together with the presently available microwave and submillimeter-wave data and ground state combination differences, were analyzed on the basis of a rotational Hamiltonian which includes Δk = ±3 and Δk = ±6 interaction terms. The derived ground state molecular parameters reproduced the transition frequencies of both allowed and “perturbation allowed” transitions within the accuracy of the measurements. The equilibrium structure was determined for the AsH₃ molecule.     

The forbidden (J → J + 1) spectrum of CH4 in the ground vibronic state

The pure rotational R-branch spectrum of CH₄ arising from the centrifugal distortion moment has been studied using a simple 12.10-m light-pipe cell and a conventional interferometer. Ten forbidden (J → J + 1) transitions for J = 7 to J = 16 have been observed in the spectral region 80–200 cm^?1 with a theoretical resolution of 0.5 cm^?1. The integrated intensity of the six strongest lines has been measured and was found to be of the order of twice that calculated from the distortion moment obtained earlier from a molecular beam study of the (J = 2) rotational level. In the approximation that frequency shifts due to this excess intensity are neglible, it has been determined that the rotational constant B₀ = (5.245 ± 0.004) cm^?1 and the scalar distortion constant D_S = (1.19 ± 0.09) × 10^?4 cm^?1. It is argued that the excess intensity is due to higher-order terms in the dipole moment operator and the validity of the frequency analysis is considered in this context.     

Intensity measurements in freon bands of atmospheric interest

The absolute intensities of the i.r. absorption bands, which are located in the atmospheric window region, of CFCl₃ (“Freon-11”) and CF₂Cl₂ (“Freon-12”) have been measured at 300°K. Our best estimates for these parameters are: for CFCl₃ (“Freon-11”), S_v = 635±36 cm^-2atm^-1 (9.2μ band), S_v = 1536±45 cm^-2atm^-1 (11.8μ band); for CF₂Cl₂ (“Freon-12”), S_v = 718±14 cm^-2atm^-1 (8.7μ band), S_v = 1136±22 cm^-2atm^-1 (9.1μ band), and S_v = 1302±40 cm^-2atm^-1 (10.9μ band).     

Moments of the spectra for rotational transitions induced by collisions or by external perturbations

Considered first is the cross sectiond σ(J′←J)/dω for the rotational transitionJ′←J of a linear rotator in collisions. The set of cross sections for a givenJ and for allJ′ defines a discrete spectral distribution as a function of the transition energy ΔE=E(J′)?E(J). In both the classical and the quantum mechanical sudden approximations the moments \(S(\mu ;J) = \sum\limits_{J'} {(\Delta {\rm E}} )^\mu d\sigma (J' \leftarrow J)/d\omega \) of ordersμ=2n andμ=2n+1 (n=0,1,...) are polynomials of degreen in the rotational energyE(J). The special cases forn=0 indicate thatS(0;J) andS(1;J) are independent ofJ. This is a theorem proved elsewhere. Explicit expressions forS(μ; J) of low orders are presented. They are derived on the assumption of equal relative velocitiesv andv′ before and after the collision. Correction onS(μ;J) for the difference betweenv andv′ is made to the lowest order in terms ofS(μ+1;J) forv=v′. The quantum mechanical results for linear rotators are extended to spherical-top and symmetric-top rotators. These results apply not only to the collision cross section but also to a physical quantity expressible in the form ¦〈Γ′¦F¦Γ〉¦² of a transition probability withany F that is independent of the initial and final rotational states ¦Γ〉 and ¦Γ′〉.     

Rotational analysis of the B-X band system of the SbO molecule

Rotational analyses of the two 0-0 bands of theB ²ΣX ²Π_reg system of SbO were carried out for the first time from spectrograms taken in the second order of a 21 ft. concave grating spectrograph having a dispersion of 1·25 Å/mm. The rotational constants of the ν=0 vibrational levels of the upper and lower states, and of the coupling constant A₀ of the lower²Π_reg state were deduced. These values are summarised below. v₀₀=25 334·93 cm^?1 B′₀=0·3190 cm^?1 B″₀=0·3490 cm^?1 A ₀=2276 cm^?1 r′₀=1·933 Å r″₀=1·848 Å.     

High-resolution FTIR spectrum of vinyl chloride: rovibrational analysis of the v 10 and v 11 fundamental bands

The Fourier transform gas-phase infrared spectra of the v ₁₀ and v ₁₁ bands of natural CH₂=CHCl have been measured with a resolution of 0.005 cm^?1 in the frequency range 820–1010 cm^?1. These vibrations of symmetry species A″ give rise to c-type bands and the transitions observed are characterized by δK _a = ±1 and δK _c = 0, ±2. Both J and K structures have been resolved in different subbranches and about 1800 (J ≤ 64, K _a ≤ 13) and 2800 (J ≤ 72, K _a ≤ 14) transitions for the v ₁₀ and v ₁₁ fundamentals, respectively, have been identified for the ³⁵Cl isotopomer. Combined analysis of the assigned data with the available ground state constants allowed the determination of the band origins, rotational and centrifugal distortion parameters for the v ₁₀ = 1 and v ₁₁ = 1 excited states of CH₂=CH³⁵Cl isotopic species. The molecular constants obtained account for slight perturbations in the v ₁₀ vibrational level.     

High-resolution FTIR spectroscopy of CHD279Br: ro-vibrational analysis of the v4 fundamental and determination of the ground state constants

The first high-resolution infrared spectrum of CHD₂⁷⁹Br has been investigated by Fourier transform spectroscopy in the range 940–1100 cm^?1 at an unapodised resolution of 0.0025 cm^?1. This spectral region is characterised by the v₄ (1036.8389 cm^?1) fundamental band, corresponding to the CD₂ wagging mode. The rotational structure of the a- and c-type components of the hybrid band has been extensively assigned for transitions involving values of J and K_a up to 65 and 15, respectively. The ground state constants up to the quartic centrifugal distortion terms have been obtained for the first time by ground state combination differences from 5251 assigned transitions and subsequently employed for the evaluation of the band origin and the excited state parameters of v₄. Watson’s S-reduced Hamiltonian in the I^r representation has been used in the ro-vibrational analysis. The dipole moment ratio |Δμ_a/Δμ_c| of the band has been estimated to be 1.3?±?0.1 from spectral simulations.     

Low temperature laser absorption spectra of methane in the near-infrared at 1.65 μm for lower state energy determination

Direct absorption spectra of the 2v₃ band of methane (CH₄) from 6038 to 6050 cm^-1 were studied at different low temperatures using a newly developed cryogenic cell in combination with a distributed feedback (DFB) diode laser. The cryogenic cell can operate at any stabilized temperature ranging from room temperature down to 100 K with temperature fluctuation less than ±1 K within 1 hour. In the present work, the CH₄ spectra in the range of 6038-6050 cm^-1 were recorded at 296, 266, 248, 223, 198, and 176 K. The lower state energy E″ and the rotational assignment of the angular momentum J were determined by a “2-low-temperature spectra method” using the spectra recorded at 198 and 176 K. The results were compared with the data from the GOSAT and the recently reported results from Campargue and co-workers using two spectra measured at room temperature and 81 K. We demonstrated that the use of a 2-low-temperature spectra method permits one to complete the E″ and J values missed in the previous studies.     

Absorption measurements of H2O at high temperatures using a CO laser

Absorption of CO laser radiation (v = 8→7, J = 14→15 transition at 1901.762 cm^-1) by H₂O has been studied in shock-heated H₂/O₂/Ar mixtures over the temperature range 1300–2300 K. This laser transition is nearly coincident with the v₂-band 12_3,10←11_2,9 transition of H₂O at 1901.760 cm^-1, thereby providing a convenient and sensitive absorption-based H₂O diagnostic useful for studies of combustion. The collision-broadening parameter for this H₂O line, due to broadening by Ar, was determined to be 2γ (cm^-1atm^-1) = 0.027 (T/1300)^-0.9 in the temperature range 1300–2300 K. Calculations of the H₂O absorption coefficient (at 1901.762 cm^-1) based on this expression for 2γ are presented for the temperature range 300–2500 K and pressure range 0.3–1 atm.     

Comment on the intensity and the temperature dependence of the nitrogen-broadened half-width of the P(6) line in the CO fundamental

The recent line-center absorption coefficient measurements on the P(6) line of the CO fundamental have been shown to be consistent with S_v(T) = 273(273/T)cm^-2atm^-1 and γ⁰(T) = 0.0652(300/T)^0.66 for the absolute intensity of the band and the nitrogen-broadened line width in the temperature range 300–800°K.     

The centimeter and millimeter microwave spectra of butadiene sulfone and α,α′-D4 butadiene sulfone

Microwave measurements on the ground and first eight excited states of the ring-puckering vibration of butadiene sulfone have been extended to millimeter wavelengths. The microwave spectra of the same vibrational states of α,α′-D₄ butadiene sulfone have been observed. For both isotopomers the Coriolis interaction between the v = 0 and v = 1 states has been analyzed to give the energy separation between these two states. These data and the variation of the rotational constants have been used to derive reduced potential functions for the ring-puckering vibration. The barrier to ring inversion is 49(2) cm⁻¹ for butadiene sulfone and 44(2) cm⁻¹ for the α,α′-D₄ isotopomer. The ring-puckering vibrational dependence of the quartic centrifugal distortion constants, including a small dependence of Δ_J and δ_J, has been accounted for.     

New analysis of the ν5 and 2ν9 bands of HNO3 by infrared and millimeter wave techniques: line positions and intensities

Nitric acid (HNO₃) plays an important role in the Earth’s atmosphere as a reservoir molecule of NO_x species. It has a strong infrared signature at 11 μm which is one of the most commonly used for the infrared retrieval of this species in the atmosphere since this spectral region coincides with an atmospheric window. It is therefore essential to have high quality spectral parameters in this spectral region. The main goal of this work is then to generate as reliable as possible line positions and intensities for the ν₅ and 2ν₉ cold bands centered at 879.1075 and 896.4467 cm⁻¹, respectively. In particular the existing line parameters need improvement in the wings of the 11 μm window in order to retrieve more accurately the CFC-11 (CCl₃F) and CFC-12 (CCl₂F₂) atmospheric species at ∼850 and ∼920 cm⁻¹, respectively. This work is also motivated by theoretical considerations. Very strong resonances couple indeed the 5¹ and 9² rotational levels. In addition the ν₉ mode (OH torsion) is a “large amplitude” motion, and torsional splittings affect both the v₉=2 and the v₅=1 rotational transitions. In the present study, these effects are accounted for simultaneously both for the line position and line intensity calculations. To calculate the line positions the Hamiltonian matrix accounts for the very strong Fermi and the weaker Coriolis interactions linking the 5¹⇔9² rotational levels, and the torsional effects are accounted for within the frame of the IAM (Internal Axis Method) approach. In addition, the v-diagonal blocks involve non-orthorhombic operators together with Watson’s type rotational operators. This means that the z-quantization axis deviates from the a inertial axis for both the 5¹ and 9² vibrational states. The line intensity calculations were performed accounting also for the axis switching effects. As far as the experimental line positions are concerned we have used the millimeter wave data available in the literature [J. Mol. Spectrosc., 175 (1996) 395; J. Mol. Spectrosc., 208 (2001) 121; and references therein], as well as new centimeter wave measurements performed in Kiel and new Fourier transform infrared spectra recorded in Giessen. For the line intensities we have used an extensive set of individual line intensities measured recently [J. Mol. Spectrosc., 218 (2003) 151]. All these experimental data were very satisfactorily reproduced using the theoretical model described above and an improved set of line positions and intensities was generated for the ν₅ and 2ν₉ bands allowing one to better model the HNO₃ absorption in the 11 μm spectral domain.