Highresolution stimulated Raman spectroscopy of methane ^{13}CD _{4} in the pentad region
Abstract
We present the first Raman spectrum of ^{13}CD _{4} recorded at room temperature in the pentad region by inverse Raman spectroscopy, thus including the ν_{1} ( A_{1}), 2 ν_{2} ( A_{1}), 2 ν_{4} ( A_{1}), and ν_{2} + ν_{4}( F_{1} + F_{2}) Q branches. It is noteworthy that the overtone bands 2 ν_{2} and 2 ν_{4} are observed for the first time in a methanelike molecule by a coherent Raman process. The wide frequency range investigated, covering 45 cm ^{1} in three parts, contains more than 300 lines with uncertainty less than 10 ^{3} cm ^{1} in most cases. These Raman data are combined with highresolution infrared data in a weighted leastsquares fit of the vibrationrotation constants of the pentad, thanks to a relevant partially reduced effective Hamiltonian including all the thirdorder interaction terms between the upper states of the five vibrational bands. These interactions within the pentad induce strong perturbations in the isotropic Raman spectrum. In particular the ν_{1} band exhibits a complex structure, which results essentially from the secondorder Coriolis interaction between the v_{1} = 1 ( A_{1}) state and the v_{2} = v_{4} = 1 ( F_{1}) state. The analysis has been realized up to J = 18 in such a way that almost all of the Raman transitions were assigned up to J = 17. These observed Raman transitions are reproduced with an overall weighted standard deviation of 1.86 × 10 ^{3} cm ^{1}, which is the order of magnitude of the accuracy of the experimental data.
 Publication:

Journal of Molecular Spectroscopy
 Pub Date:
 January 1988
 DOI:
 10.1016/00222852(88)900161
 Bibcode:
 1988JMoSp.127..156M