The torsional dependence of the dipole moment operator in methyl silane

Infrared and Millimeter-Wave Study of the Four Lowest Torsional States of CH3CF3

“…Although the spectra were heavily blended, -splittings on the order of 0.03 cm Ϫ1 were identified. The origin of the (v 6 ϭ 2 4 0) band was determined to be 423.150 (15) cm Ϫ1 , in agreement with the earlier, less accurate determination of 423.25 cm Ϫ1 made in a lower resolution study of this band (5). From the intensity analysis of the torsional overtone, the effective transition dipole moment 0,eff T has been determined.…”

“…The synthesis of the theoretical spectrum for the torsional bands of a G 18 molecule has been discussed for CH 3 SiH 3 (15). The matrix elements of the space-fixed components of the dipole operator driving these transitions can be taken from the standard C 3v expressions for a parallel band (16) by replacing the usual dipole constant with an effective dipole-moment function; see, in particular, Eq.…”

“…[4] of Ref. (15). For the (v 6 ϭ 2 4 0) band of CH 3 CF 3 , this function can be written in the hybrid approach as follows,…”

“…If H T can be approximated by H T 0 and if the only information available is derived from intensity measurements of nonresonant torsional bands, it is not possible to determine 0 T and 2 T independently (15). In this case, one can set 2 T ϭ 0 and account for the intensities with a single effective moment:…”

“…[21], the matrix elements are the diagonal analogues in the zeroth-order basis of the off-diagonal elements defined in the higher-order basis in connection with Eq. [15]. When the higher-order terms are taken into account, Eq.…”