Jacques Dupre

The infrared bands ν2 and ν5 of CH3Br with Coriolis interaction

Abstract The infrared bands ν 2 and ν 5 of CH 3 Br have been measured at a resolution of 0.015 cm −1 . The lines due to the isotopic species CH 3 79 Br and CH 3 81 Br were resolved and altogether about 3000 lines were assigned. The bands were analyzed simultaneously by taking into account the xy -Coriolis resonance between the states v 2 = 1 and v 5 = 1. A local perturbation observed in ν 5 could be explained in terms of a (1,−2) resonance between v 2 = 1 and v 5 = 1. Some perturbation allowed transitions could be assigned and they give an equation between A 0 and D 0 K .

Absorption spectrum of trideuteromethane between 7 and 11 μm. Analysis of the ν5 band

Abstract The absorption spectrum of trideuteromethane was recorded in the range 900–1400 cm−1 with a resolution of 0.020–0.025 cm−1. The ν5 band centered at 1292.499 cm−1 is analyzed here. A fit based on 869 observed transitions including J′ values up to 22, leads to a set of spectroscopic constants suitable for energy calculations in the upper-state v5 = 1. These constants reproduce the experimental wavenumbers with a standard deviation equal to 0.008 cm−1. The tabulated line strengths are calculated on the basis of the value S = 27.1 cm−2 atm−1 at 300 K, measured by Hiller and Straley, for the band strength of ν5. A useful comparison is made between the values now derived for some constants and the corresponding ones predicted by Gray and Robiette in their recent force field calculations of methane and isotopic species.

A complete study of the v 1, v 2, 2v 2 bands of ClCN with their associated hot bands

The 378 cm-1 and 780 cm-1 bands of ClCN, have been remeasured with a resolution of about 0·002 cm-1, using a Bruker Fourier transform spectrometer. Sixteen transitions in the region of the v 2 band and twenty in the region of the v 1 and 2v 2 bands have been analysed for 35ClCN and 37ClCN. The Fermi resonance between the states |v 1, v 2, l 2, v 3> and |v 1 - 1, v 2 + 2, l 2, v 3> has been investigated. The accuracy of the calculated band origins is better than 0·0003 cm-1 for most bands. New molecular constants are obtained.

IR high-resolution spectroscopy of the ν3 and ν6 modes of CH3F and CD3F isolated in nitrogen and neon matrices: Intramolecular V-V transfer

Abstract After some general considerations about the different contributions to the linewidths observed in infrared for matrix isolated molecules, the case of the ν 3 and ν 6 modes of CH 3 F and CD 3 F in nitrogen and neon matrices is discussed. When reducing the inhomogeneous contributions by annealing and dilution, the higher of these two modes remains at least three times larger than the lower. The temperature effect on these linewidths is consistent with an intramolecular energy transfer, assisted by the lowest vibrational mode of the solid nitrogen at 32 cm −1 .

High-resolution analysis of the ν3 and ν6 bands of CD3Cl

Abstract This paper describes the analysis of the ν 3 and ν 6 fundamental bands of methyl chloride d 3 using a high-resolution spectrum (resolving power of the apparatus: 0.0015 cm −1 ). These bands are coupled by a weak Coriolis interaction and are then treated simultaneously. Spectroscopic constants are derived for the two isotopic species CD 3 35 Cl and CD 3 37 Cl.

Modele theorique de separation isotopique par laser

Abstract The energy transfer reactions involved in the isotope separation of molecular mixtures by selective two-step photodissociation are discussed. Results of computer experiments show the validity of the theoretical model. Isotope enrichment may he predicted.

Passive Ǫ switching of a CO2 laser by allene molecule

Abstract Passive O switching of a CO2 laser was observed using allene gas. Investigation of the high-resolution spectrum of allene in the spectral range of 9.8 μm gives the assignment of the pulsing line as being RR2 (23) of ν9 transition.

Approaches to dissociation processes of SF6 by one or two T.E.A. CO2 lasers

Abstract We present experimental results on the variation of the SF6 dissociation rate as a function of the frequency and energy of the CO2 T.E.A. laser. We give a possible explanation of dissociation by classical absorption mechanisms involving ΔJ = ±2 transitions, and we present a process that we call “probabilities-crossing mechanism”.