BARRIER TO INTERNAL ROTATION IN METHYL $STANNANE^{*}$

Abstract

The microwave spectrum of methyl stannane has been $reinvestigated.^{1}$ Ground state transitions for $J = 0\rightarrow 1$ were measured for seven tin isotopes (116 to 124). Three torsional states for each of the 116, 118 and 120 isotopes were observed to be split into doublets due to vibration-internal rotation interaction, and their frequencies were fitted to Kivelson’s $equation^{2}$ \[ \nu/2 ={B_{v}+G_{v}<m|\pi^{2}|m>+F_{v}< m|1-\cos 3 \theta|m>} \] Values $F_{v} =--17.568$ mc. And $G_{v} =--0.3525$ mc, were obtained, from which the torsional satellites of all the isotopes were calculated and agreed to within 0.3 mc. with observed transitions. From the observed splittings of the torsional states a barrier of $650 \pm 30$ calories was calculated. Correlations between molecules in this series will be discussed.