Jean-Claude Deroche

High resolution infrared spectrum of CH2D2: The ν1 and ν6 fundamental bands near 3000 cm−1

Abstract The spectrum of CH 2 D 2 between 2865 and 3165 cm −1 has been investigated under high resolution with a Fourier-transform interferometer. Two fundamental bands have been analyzed, the B-type band ν 1 and the C-type one ν 6 . These two bands are more or less perturbed. It was possible to compute more than 1100 ground-state combination differences. These 1100 data allowed the determination of ground-state constants: A o = 4.3027777(38), B O = 3.5058838(35), C O = 3.0500599(37), Δ J = (0.46419 ± 17)10 −4 , Δ JK = (−0.15781 ± 58)10 −4 , Δ K = (0.72997 ± 60)10 −4 , δ J = (0.088372 ± 90)10 −4 , δ K = (−0.14948 ± 64)10 −4 (all in cm −1 ). We obtained a standard deviation of 0.0008 cm −1 .

The ν5 and ν3 Raman bands of CH2D2

Abstract The ν5 and ν3 Raman bands of CH2D2 have been recorded with a resolution of 0.35 cm−1. The ν3 state is well known from infrared studies. Three hundred twenty-nine transitions of the ν5 band were analyzed, assuming an unperturbed upper state, giving a standard deviation on the fit of the upper-state energies of 0.037 cm−1, The constants A, B, C, ΔJ, ΔJK, and ΔK differed significantly from the ground-state values, and ν5 was determined as 1331.41 ± 0.05 cm−1. This work represents the first complete analysis of the fine structure of a rotation-vibrational Raman band for an asymmetric rotor. The ν5 state could not be analyzed in infrared so this investigation, once more, demonstrates the usefulness of the Raman method.

Resonances and doublings in the infrared spectrum of CH3D at 9ų

Abstract The spectrum of CH 3 D has been studied between 1040 and 1280 cm −1 with a Czerny-type spectrometer having a resolving power of 0.1 cm −1 . In the perpendicular ν 6 band, a strong l -type doubling is taking place. In addition it is necessary to introduce a resonance of the type l (2, 2). Further improvement of the calculation is obtained by using an energy expansion including the third order correction E 3 = kl [ η 6 J J ( J + 1) + η 6 K k 2 ]. We have determined the values of η 6 J and η 6 K which are surprisingly large compared to the D constants. A Coriolis interaction between ν 6 and the parallel ν 3 band (centered near 1307 cm −1 ) has been investigated. In spite of the small value of the coupling coefficient ζ 3,6 x , the existence of this resonance is unquestionable. Moreover, a K -type doubling in the P P 3 and P Q 3 branches was analysed and the corresponding γ coefficient was evaluated.

Assignments of submillimeter emissions in difluoromethane pumped by12C18O2 and12C18O2 lasers

A FT spectrum of υ3, υ9 and υ7 of CH2F2 is recorded and assigned between 1030 and 1230 cm−1. Coincidences with CO2 lasers are investigated.Submillimeter emissions are unambiguously assigned by a loop procedure including only IR and SMM measurements. In some cases pseudo-loops are added using ground state computed energies. In spite of the large perturbations, an exact model for excited vibrational states is not needed to ascertain SMM assignments.

High-resolution infrared spectrum of CH2D2: The ν3 fundamental band at 7 μm

Abstract The infrared spectrum of CH 2 D 2 has been recorded in the region of 1345 to 1561 cm −1 with a resolution of 0.030 to 0.026 cm −1 . Most of the observed lines have been assigned to transitions of the ν 3 band of CH 2 D 2 . However, 114 lines have been identified as transitions of the ν 2 band of H 2 16 O whose band origin has been directly determined to be 1594.7472 ± 0.0030 cm −1 . A few weak lines, probably belonging to the ν 5 fundamental of CH 2 D 2 , remain unassigned. The band center ν = 1435.1326 ± 0.0030 cm −1 and a set of upper state constants were obtained for the ν 3 band of CH 2 D 2 . Although a slight perturbation was noticed in the ν 3 band, all wavenumbers have been fitted with a standard deviation of 3.8 × 10 −3 cm −1 .