THE INFRARED SPECTRUM OF TRIDEUTEROSILANE AND THE INTERNUCLEAR DISTANCE IN SILANE

Abstract

Trideuterosilane has been prepared by the action of lithium aluminum deuteride on trichlorosilane. A parallel absorption band at $4307 cm^{-1}$, which corresponds to the first overtone of the Si-H stretching vibration, has been studied with a high-resolution infrared spectrometer. The rotational lines up to $J = 25$ have been observed and much of the K structure has been resolved. Although the upper state is slightly perturbed, it has been possible to assign most of the rotational structure and obtain from it the rotational constants of the ground state. $B_{0}$ was found to be $1.7755 \pm 0.0008$ $cm^{-1}$, which corresponds to a Si-H internuclear distance of $1.4798 \pm 0.0004 A$ if it is assumed that $r_{0} (Si-H) = r_{0} (Si-D)$ and that the angles are tetrahedral. This value for the Si-H internuclear distance in silane is somewhat greater than the value of 1.456A accepted at present.