Millimeter-Wave Spectra of CH3SiH3in the Two Interacting Torsional States (v12= 0,v6= 3) and (v12= 1,v6= 0)

High-Resolution Far-Infrared Torsional Spectrum of CH3SiD3 Using a Synchrotron Source

“…For the gs of CH 3 SiD 3 , it was found here that the barrier height V 0,3 = 583.94102(59) cm −1 . For the gs of CH 3 SiH 3 , the barrier height obtained from a similar two band gs/ν 12 analysis was V 0,3 = 591.4107(26) cm −1 (7). The decrease in barrier height upon full deuteration of the silyl top is ∼7.5 cm −1 .…”

The ν12 Band of CH3SiD3

“…There are now four symmetric-top molecules with a largeamplitude internal degree of freedom for which a global highresolution analysis of a perturbed vibrational band was carried out: the current work on CH 3 SiD 3 , along with previously reported analyses for CH 3 SiH 3 (3,2,4), CH 3 CD 3 (5), and ethane (6). Comparison of the results between the protonated and deuterated species and between symmetric tops containing different heavy atoms coupled with more sophisticated ab initio calculations will lead to a fuller understanding of the coupling mechanisms that are involved and should advance our understanding of the vibration-torsion-rotation effects in both symmetric and asymmetric tops.…”

“…For example, in the ground torsional state v 6 ϭ 0 of the ground vibrational state (gs) of CH 3 SiD 3 , the torsional splitting is on the order of 200 MHz (1). However, in the zero-point torsional state of the lowest frequency vibrational fundamental, unusually large -splittings were observed for CH 3 SiH 3 (2)(3)(4), CH 3 CD 3 (5), and CH 3 CH 3 (6). This effect was attributed to Coriolis-type coupling between the stacks of torsional levels in the two different vibrational states.…”

“…The 12 band of CH 3 SiD 3 is essentially a perpendicular fundamental band in a C 3v molecule, but with additional fine structure arising from the internal rotation (2)(3)(4). Following the discussion in Section III of Ref.…”

“…The lowest frequency fundamental band is the most favorable one for investigating this coupling, since it can be confidently assumed that levels in this vibrational state are only significantly perturbed by the torsional stack of the ground vibrational state (2). An accurate determination of this coupling and a very stringent test of the vibration-torsion-rotation Hamiltonian were made for CH 3 SiH 3 (2)(3)(4). This was made possible by the presence of a very extensive data set which sampled many of the torsional levels in the gs as well as the (v 12 ϭ 1, v 6 ϭ 0) state.…”