Band analysis of the Swan system (d3Πg-a3Πu) of 13C2 and 12C13C molecules

The emission spectrum of the d³Π_g-a³Π_u system (Swan bands) due to ¹³C₂ and ¹²C¹³C molecules has been obtained in a low pressure hollow cathode discharge through a mixture of argon and benzene containing enriched ¹³C (90%). The spectrum was photographed on a 3.4-m Ebert spectrograph (reciprocal dispersion 0.54 Å mm^?1 in the first order). Isotope effect measurements have been carried out to determine the shift between isotopic bands and those emitted by ordinary molecules. The rotational analysis of six ¹³C₂ bands and three bands of ¹²C¹³C has been performed and molecular constants were derived.     

The vibration-rotation spectrum of methinophosphide: l-Type doubling, l-type resonance and the ν2, 2ν2, and 3ν2 bands of H12CP; The ν1 and ν2 bands of H13CP

The vibration-rotation bands ν₂, 2ν₂, and several “hot” bands of H¹²CP have been recorded and assigned. The states with v₂ = 2, perturbed by l-type resonance and l-type doubling effects have been analyzed on the basis of the existing theory. The energy difference between the 02²0 and the 02⁰0 states was found to be 17.5095 (19) cm^?1. Because of insufficient data, the states with v₂ = 3 could not be corrected for l-type resonance interaction and therefore only an effective l-type doubling constant was obtained. The ν₁ and ν₂ bands of the H¹³CP isotopic molecule (present at natural concentration) were also identified and their spectroscopic constants obtained. The value of I_e for H¹²CP is found to be 25.18793 (26) amu Ų.     

Analysis of the ν2 + ν3 band of 12CH4 and 13CH4

The ν₂ + ν₃ bands of ¹²CH₄ and ¹³CH₄ occurring in the region 4400–4650 cm^?1 have been studied from spectra recorded with a high-resolution Fourier transform spectrometer (resolution better than 0.01 cm^?1). Champion's Hamiltonian expansion, Canad. J. Phys.55, 1802 (1977), is applied to the problem of the two interacting F₁ and F₂ vibrational sublevels of this type of a band. As the P branch of ν₂ + ν₃ is strongly overlapped by neighboring bands, a combination-difference method, adapted to tetrahedral XY₄ molecules has been developed to help assignments of lines. A fit of 700 transitions has been performed using 13 new effective constants in the case of ¹²CH₄. In the case of ¹³CH₄, 532 transitions have been fit to 18 constants. The known parameters, relative to the vibrational ground state and the ν₃ state for both methanes, and the ν₂ state for ¹²CH₄ were fixed throughout. Most of the perturbed levels, up to J′ = 12, are well reproduced and the general agreement between experimental and calculated transitions is satisfactory with standard deviations of 0.047 cm^?1 (¹²CH₄) and 0.041 cm^?1 (¹³CH₄). The results (order of magnitude of obtained (ν₂ + ν₃) parameters and comparison of observed and computed intensities) indicate that the ν₂ + ν₃ band is perturbed by many other bands.     

High-resolution diode laser spectra of the ν4 mode of 12CF3I and 13CF3I

High-resolution spectra of the ν₄ mode of ¹²CF₃I and ¹³CF₃I have been recorded using diode laser spectroscopic techniques. The sample was cooled to 163 ± 10 K to suppress the hot bands. Natural CF₃I containing 98.9% ¹²CF₃I and 1.1% ¹³CF₃I was used for recording the spectra. About 1200 lines in the P and R branches of each isotopic molecule have been assigned and used in the least-squares fit. The pseudoparallel structure of the bands has been understood and accurate values of rotational constants have been obtained.     

The high-resolution infrared spectrum of the ν10, ν14, and ν13 bands in allene-1,1-d2

The perpendicular bands ν₁₀, ν₁₄ and ν₁₃ of allene-1,1-d₂, which are located in the region 550–950 cm^?1, have been studied from their infrared spectra at a resolution near 0.0045 cm^?1. High-quality ground state constants have been determined from ν₁₀ and ν₁₃. The three bands are perturbed by a number of Coriolis and vibrational resonances, and rotation-vibrational constants are derived for the ν₁₀, ν₁₄, and ν₁₃ levels using two models to include such interactions. One of them accounts for type-a Coriolis and vibrational resonances between the four levels ν₁₀, ν₁₄, ν₁₃, and ν₉ using the full asymmetric rotor model of Watson. The other model is based on the symmetric top approximation and includes type-b and -c Coriolis interactions with the ν₃ and ν₄ levels, in addition. A preliminary discussion of resonances in the weak ν₉ band and an identification of the hot bands ν₁₁ + ν₁₀ ? ν₁₁, ν₁₅ + ν₁₀ ? ν₁₅, ν₁₁ + ν₁₃ ? ν₁₁, and ν₁₅ + ν₁₃ ? ν₁₅ is also presented.     

The infrared spectra of 12C32S, 12C34S, 13C32S,and 12C33S

Using a tunable diode laser spectrometer, the infrared absorption spectra of four isotopic species of carbon monosulfide have been observed in the positive column of a dc discharge of CS₂ and Ar. The wavenumbers of 115 vibration-rotation transitions between 1180.5 and 1266.1 cm^?1 have been measured. These lines were assigned to the 1-0, 2-1, 3-2, and 4-3 bands of ¹²C³²S, the 1-0 and 2-1 bands of ¹²C³⁴S and ¹³C³²S, and the 1-0 band of ¹²C³³S. These new data have been combined with the previous infrared and microwave results to determine Dunham coefficients (Y_ij), the Dunham potential expansion constants (a₀,a₁,a₂,a₃, and a₄), and the classical turning points by the RKR method.     

Cr3+−Cr3+ excited state Raman scattering from molecular vibrations in binuclear Cs3Cr2Cl9 induced by exchange striction

On increasing the temperature, several new bands appear at higher energy from their parent vibrational modes in the Raman spectrum of the molecular complex Cr₂Cl^3?₉. The parent and new bands have intensities that follow the thermal population factors of various ⁴A_2g⁴A_2g Cr³⁺ pair states. This behaviour is attributed to exchange striction which produces a change in vibrational energy with excited state for those normal modes with large net axial Cr³⁺?Cr³⁺ displacements.     

Analysis of the ν2 and ν4 infrared bands of CD4

The infrared spectrum of totally deuterated methane CD₄ has been recorded between 930 cm^?1 and 1180 cm^?1 under high resolution (0.003 cm^?1). The ν₂ and ν₄ bands of ¹²CD₄ have been reanalyzed on the basis of a complete third-order Hamiltonian including all the coupling terms linking the upper states of the two bands. A set of only 16 self-consistent parameters have been adjusted to fit more than 1650 assigned transitions reaching a maximum upper state J value of 20. The obtained standard deviation is 0.0041 cm^?1. In addition, 171 lines of the ν₄ band of ¹³CD₄ have been assigned. They have been analyzed, in the same dyad scheme, by adjusting 7 parameters of the ν₄ band together with the main ζ₂₄ Coriolis parameter. The obtained standard deviation is only 0.0012 cm^?1.     

Coherent Stokes and anti-Stokes Raman spectra of the ν1 (A1) and ν2 (E) bands of SF6 and UF6

Coherent Stokes and anti-Stokes Raman scattering are used to study the ν₁ and ν₂ spectral band profiles of UF₆ and SF₆. Most of the observed SF₆ “hot” bands are assigned, leading to evaluations of the anharmonicity constants X_ij: X₁₂ = ?(2.80 ± 0.30) cm^?1, X₁₄ = ?(1.00 ± 0.15) cm^?1, X₁₅ = ?(1.00 ± 0.15) cm^?1. For UF₆, a tentative assignment of the “hot” bands is made: X₁₂ = ?(1.80 ± 0.30) cm^?1, X₁₃ = ?(1.60 ± 0.30) cm^?1, X₁₄ = ?(0.20 ± 0.10) cm^?1, X₁₅ = ?(0.25 ± 0.10) cm^?1, and X₁₆ = ?(0.10 ± 0.05) cm^?1. Parameters such as the vibration-rotation coupling constants are determined. For SF₆: α = (7 ± 2) × 10^?5 cm^?1 for the ν₂ band and α = ?(1.02 ± 0.01) 10^?4 cm^?1 for the ν₁ band. The calculated spectral profiles of the coherent Stokes or anti-Stokes spectra, which are in good agreement with experimental results, give values for the resonant and nonresonant parts of the susceptibility in both molecules. They also show, in some cases, the influence of neighboring combination bands.     

13C16O2, 13C18O2: Emission spectra in the 4.5-μm region

In this paper the same kind of results are given for ¹³C¹⁶O₂,and ¹³C¹⁸O₂ as for ¹²C¹⁸O₂ [D. Bailly and C. Rossetti, J. Mol. Spectrosc.105, 215–228 (1984)]. Forty seven vibrational bands are analyzed from which spectroscopic constants are computed. These constants reproduce wavenumbers with a RMS of the order of 3 × 10^?5 cm^?1 for the best measurements. For each species, a set of molecular parameters is given for Σ-Σ transitions.     

Infrared spectrum of isotopic carbon dioxide in the region of bending fundamental ν2

Infrared absorption spectra of ¹³C¹⁶O₂, ¹³C¹⁸O₂, ¹⁶O¹³C¹⁷O, ¹⁶O¹³C¹⁸O, and ¹⁶O¹²C¹⁸O have been measured in the wavenumber region 570–780 cm^?1 with a spectral resolution of about 0.005 cm^?1. The data were recorded at room temperature with a Fourier transform spectrometer using a ¹³C-enriched sample of carbon dioxide. The fundamentals ν₂ and several “hot” bands have been identified and effective molecular constants have been derived.     

Raman intensity measurements of the Fermi diad ν1, 2ν2 in CO2 and CO2

Intensity measurements of the ν₁, 2ν₂ vibrational Raman bands of ¹²CO₂ and ¹³CO₂ lend support to Amat's suggestion that the unperturbed 02⁰0 level is above the 10⁰0 level for ¹²CO₂. For ¹³CO₂, however, the ordering of the levels is reversed.     

The infrared spectra of SiH3F: ν3 and ν4 bands

Infrared spectra of silyl fluoride were recorded at a resolution of 0.06 cm^?1 using a Nicolet Fourier transform interferometer. Analyses of the ν₃ and ν₄ bands are presented for ²⁸SiH₃F, together with work on ²⁹SiH₃F, ³⁰SiH₃F, and various hot bands.     

Improved rovibrational constants and frequency tables for the normal laser bands of 12C16O2

New frequency difference measurements between Doppler-free stabilized laser lines in the 9.4- and 10.4-μm bands of ¹²C¹⁶O₂, including high-J and across-the-band-center measurements, have made significant improvements in the rovibrational constants. The absolute frequencies were referred to the methane stabilized 3.39-μm HeNe laser. Frequency tables generated from these constants have absolute uncertainties of less than two parts in 10¹⁰ and are about a factor of 10 better than older tables. In addition, the laser lines P_I(50) in ¹³C¹⁶O₂ and R_II(26) in ¹³C¹⁸O₂, which were used as reference lines in recent visible laser frequency measurements, were also measured to about the same accuracy.     

The Infrared Spectrum of CCH2: The Bending States up to v4+v5=4

The vibration-rotation spectra of ¹³C monosubstituted acetylene, ¹²C¹³CH₂, have been recorded in the region between 450 and 3200 cm⁻¹ with an effective resolution ranging from 0.004 to 0.006 cm⁻¹. A total of about 5300 rovibrational transitions have been assigned to 53 bands involving the bending states up to v_t=v₄+v₅=4, allowing the characterization of the ground state and of 30 vibrationally excited states. All the bands involving states up to v_t=3 have been analyzed simultaneously by adopting a model Hamiltonian which takes into account the vibration and rotation l-type resonances. The derived spectroscopic parameters reproduce the transition wavenumbers with a RMS value of the order of the experimental uncertainty. Using the same model larger discrepancies between observed and calculated values have been obtained for transitions involving states with v_t=4. These could be satisfactorily reproduced by only adopting, in addition to the previously determined parameters which were constrained in the analysis, a set of effective constants for each vibrational manifold.     

Line positions and intensities for the ν1 + ν2 and ν2 + ν3 bands of H218O

The intensities of about 90 lines of the ν₁ + ν₂ and ν₂ + ν₃ bands of H₂¹⁸O have been measured using a Fourier transform spectrum of natural water vapor. The constants involved in the rotational expansion of the transformed transition moment operators corresponding to these bands have been determined through a fit of these line intensities. The constants obtained are used to compute the whole spectrum of the ν₁ + ν₂ and ν₂ + ν₃ bands of H₂¹⁸O providing reliable line positions and intensities. For lines involving perturbed levels a comparison is given with the results obtained for H₂¹⁶O and it is shown that the results for one isotopic species cannot be transferred directly to another one.     

Laser Stark spectroscopy of methyl cyanide in the 10-μm region: Analysis of the ν4 and ν7 bands,and the ν7, 3ν81 interaction

About 550 Stark tuned resonances of the ν₄ and ν₇ vibration-rotation bands of CH₃CN were measured using ¹²CO₂, ¹³CO₂, and N₂O lasers. These data are combined with 26 microwave measurements and fitted to a model which includes l-type doubling in ν₇, ν₄-ν₇ Coriolis coupling, and ν₇-³ν₈¹ Coriolis and Fermi couplings. The infrared and microwave data can be reproduced with standard deviations of 7 MHz and 40 kHz, respectively. The many vibration-rotation parameters and the dipole moments are determined with great accuracy. A complete list of derived parameters is given in Table I.     

Acetylene spectra with a tunable diode laser: (ν4 + ν5)0+−ν41fQ branches of 12C2H2 and 12C13CH2

The rotational structure of the Q branches of the (ν₄ + ν₅)⁰⁺?ν₄^1f bands of ¹²C₂H₂ and ¹²C¹³CH₂ at 13.7 μm has been observed in a natural sample of acetylene by using a tunable diode laser as a source in a high-resolution infrared grating spectrometer equipped with a precision grating drive. Altogether 23 lines from J = 6 to 28 for ¹²C₂H₂ and 15 lines from J = 6 to 20 for ¹²C¹³CH₂ have been identified. The observed full width at half maximum of the resolved lines of these Q branches is very close to the calculated Doppler width. Molecular constants ν₀ + B″, B′ ? B″ ? 2D″, D′ ? D″, and H′ ? H″ have been derived from the measured line positions of the rotational structure.     

Study of isotopic 13C2 bands of the Deslandres-D'Azambuja system

The emission bands of the Deslandres-D'Azambuja system of ¹³C₂ have been obtained in the region 320–450 nm using a source containing enriched ¹³C. Measured line positions of the 2-0, 2-1, 1-0, 0-0, 1-1, 1-0, 2-1, and 3-2 bands were fitted by a least-squares procedure to determine the rotational constants and the origin for each band. The fitted origins were used as input in calculation of the vibrational constants for both C¹Π_u electronic states involved in the transition.     

Higher overtones of the bending vibrations of the ground states of 12CS2 and 13CS2

Large numbers of ‘hot’ bands in the first electronic absorption systems of ¹²CS₂ and ¹³CS₂ have been analyzed from plates taken at high dispersion, and accurate rotational constants have been obtained for the overtones of the ground state bending vibration up to v₂ = 6 and l = 3 for ¹²CS₂ and v₂ = 4, l = 2 for ¹³CS₂. The energy differences between the various levels with the same l value have been determined to an accuracy of about ±0.006 cm^?1, but (because of the parallel polarization of the electronic transition) the absolute energies of levels with l > 0 cannot be obtained.