A. Cabana

Analysis of the v 3 and v 1 infra-red bands of SiH4

The high-resolution infra-red spectrum of SiH4 in the region 2101 cm-1 to 2265 cm-1 has been analysed. Most of the lines observed have been assigned to transitions of the v 3 and v 1 bands of the abundant isotopic species 28SiH4. The v 1 band is formally forbidden in the infra-red, but a vibration-rotation interaction between v 1 and v 3 lends intensity to the v 1 transitions. The spectrum has been fitted by diagonalizing the v 3 = 1 and v 1 = 1 hamiltonians coupled by the vibration-rotation interaction term. 500 transitions have been fitted with an overall standard deviation of 0·007 cm-1, using only 15 adjustable parameters (ten in the v 3 = 1 hamiltonian, four in the v 1 = 1 hamiltonian, and one interaction coefficient). The calculated intensities are also in good agreement with experiment. Transitions of the other isotopic species 29SiH4 and 30SiH4 have also been observed, but these spectra have not been analysed in detail.

The vibration-rotation spectrum of methinophosphide: The overtone bands 2ν1 and 2ν3, the summation bands ν1 + ν2 and ν2 + ν3, and the difference band ν1 - ν2

Abstract The vibration-rotation bands 2 ν 1 , 2 ν 3 , ν 1 + ν 2 , ν 2 + ν 3 , and ν 1 - ν 2 of H 12 CP were recorded and analyzed. These data were combined with previously reported results for this molecule to obtain an improved and extended set of vibrational and rotational constants. All x ij and γ ij were calculated except those that require data from a summation band involving ν 1 and ν 3 .

High-resolution infrared spectrum of the ν3 and ν2 + ν3 − ν2 bands of 14N16O2

Abstract The infrared absorption spectrum of the ν 3 band of 14 NO 2 has been recorded with a resolution and a frequency accuracy much improved over the previous investigations. The K - and N -line assignments have been greatly extended and a more accurate set of spectroscopic constants derived. Several lines in the subbands with K a ≥ 3 have been observed to be doubled by spin-rotation interaction and spin-rotation interaction constants have been obtained. Several weak series of lines in the spectrum ( K a = 0, 1, 2, and 3) have been unambiguously assigned to the “hot band” ν 2 + ν 3 − ν 2 . Lines of the K a = 3, 4, 5, and 6 sub-bands of ν 3 have been found to be perturbed by a Coriolis interaction with the K a = 4, 5, 6, and 7 levels of 2 ν 2 .

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

Abstract The vibration-rotation bands ν 2 , 2 ν 2 , and several “hot” bands of H 12 CP have been recorded and assigned. The states with v 2 = 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 02 2 0 and the 02 0 0 states was found to be 17.5095 (19) cm −1 . Because of insufficient data, the states with v 2 = 3 could not be corrected for l -type resonance interaction and therefore only an effective l -type doubling constant was obtained. The ν 1 and ν 2 bands of the H 13 CP isotopic molecule (present at natural concentration) were also identified and their spectroscopic constants obtained. The value of I e for H 12 CP is found to be 25.18793 (26) amu A 2 .

The infrared spectrum of diacetylene

Abstract The spectrum of diacetylene has been investigated with high resolution in both the infrared and photographic infrared regions. Bands at 628, 1241, 9609, and 9717 cm −1 have been rotationally analyzed for the first time, and bands at 8578, 8744, and 9684 cm −1 have been reinvestigated with higher resolution than in earlier work. Improved rotational constants have been obtained for the ground state, viz., B ″ 0 = 0.14640 6 ± 0.00002 cm −1 and D ″ 0 = (1.0 ± 1.0) × 10 −8 cm −1 . The error limits are dominated by systematic errors rather than statistical errors and are dependent on the general lack of resolution of the “cold” bands from the underlying “hot” bands. Molecular constants have been derived for several vibrational levels. In particular, the l -type doubling in the ν 9 level has been shown to be smaller than in earlier work. The rotational constants for the ν 7 level have been accordingly revised. Accurate molecular constants for the ν 8 level are reported for the first time. The new data permit predictions of the frequencies of the ( ν 8 − ν 6 ) difference band, which lies in the microwave region of the spectrum. The ( ν 6 + ν 8 ) combination band at 1241 cm −1 is unusually strong and may serve as a useful probe for diacetylene in astrophysical sources.

The ν1 and ν1 + ν2 − ν2 infrared absorption bands of H12CP

Abstract The vibration-rotation spectrum of HCP was recorded in the region of the ν1 band with a resolution of about 0.035 cm−1. All the data available were combined to calculate spectroscopic constants for the 0000, 1000, 011e0, 011f0, 111e0, and 111f0 states.

High resolution infrared measurements on the ν3 vibration-rotation band of 28SiH4

Abstract The ν 3 vibration-rotation band of silane ( 28 SiH 4 ) has been measured at high resolution (0.030–0.045 cm −1 ). The tetrahedral splitting has been partially resolved. The analysis of the band has yielded an improved set of molecular constants.

The 4ν2 + ν3 band and the general quartic force field of CS2

Abstract The 4ν 2 + ν 3 band of 12 C 32 S 2 has been remeasured and the band origin has been determined to be at 3129·980 cm −1 . This value is in agreement with the estimate by Blanquet and Courtoy and in conflict with the earlier value used by Smith and Overend in the determination of the force constants in the general quartic valence force field of CS 2 . Accordingly the force constants of CS 2 have been recalculated using the revised value for the energy of the 04°1 vibrational state and incorporating new data for the states 30°1, 22°1 and 10°3 from the measurements of Blanquet and Courtoy.

High resolution infrared spectrum of the ν1 band of 14N16O2

Abstract The infrared spectrum of the ν 1 band of 14 N 16 O 2 has been recorded with a resolution of about 0.025 cm −1 in the region extending from 1480 to 1270 cm −1 . From about 1350 cm −1 , the absorption became progressively weaker and no absorption at all could be detected below the band origin located at 1319.797 cm −1 . Because series with low values of K a could not be measured, constants which depend strongly upon the molecular asymmetry could not be determined.

The vibration-rotation spectrum of DCP: The analysis of the fundamental bands ν1 and ν2, of the overtone band 2ν1, of the summation band ν1 + 2ν3, and of the difference band ν1 - ν2

Abstract The vibration-rotation bands ν1, ν2, ν1 - ν2, ν1 + 2ν3, and 2ν1 have been recorded and analyzed. A simultaneous fit of 395 transitions, including those previously known, was made to obtain improved spectroscopic constant for D12CP in 6 different vibrational states.