Millimeter Wave Spectra of AsH3and AsD3

The $J=0\mathrm{}\to 1$ rotational transitions of As${\mathrm{H}}_3$ and of As${\mathrm{D}}_3$ have been measured in the one to three millimeter wave region. The $B_0$ values obtained are, in Mc/sec: 112 468.46 for ${\mathrm{As}}^{75}$ ${\mathrm{H}}_3$ and 57 477.15 for ${\mathrm{As}}^{75}$ ${\mathrm{D}}_3$. The observed nuclear quadrupole coupling, $\mathrm{eQq}$, of ${\mathrm{As}}^{75}$ differs for the two species and is -160.1±0.4 Mc/sec for ${\mathrm{As}}^{75}$ ${\mathrm{H}}_3$ and -165.9±0.4 Mc/sec for ${\mathrm{As}}^{75}$ ${\mathrm{D}}_3$. Detectable ${\mathrm{As}}^{75}$ nuclear magnetic interaction was found with the magnetic coupling constant $A=0.33\mathrm{}$ Mc/sec for As${\mathrm{H}}_3$ and $A=\sim 0.07$ Mc/sec for As${\mathrm{D}}_3$. From a consideration of previous microwave work on As${\mathrm{H}}_2$D and a consideration of the differences in the bond angles in normal and deuterated stibine, the bond angle in As${\mathrm{H}}_3$ is assumed to be 91°50′ and that in As${\mathrm{D}}_3$ to be 91°31′. These angles with the observed moments of inertia yield the value 1.5192 A for the As-H length and 1.5145 A for the As-D length.