Submillimeter-Wave Spectra of Ammonia and Phosphine

Abstract

Rotational transitions of different isotopic species of ammonia and phosphine have been observed in the ½- to 1-mm region. The frequency of the $J=0\mathrm{}\to 1$ transition of ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ ${\mathrm{H}}_3$ is 572 496.69 ± 0.60 Mc/sec and that for ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$ ${\mathrm{H}}_3$ is 572 053.18 ± 0.50 Mc/sec. Spectral constants $B_0$ observed for the different isotopic species (in Mc/sec) are: 298 114.68 for ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ ${\mathrm{H}}_3$, 297 359.32 for ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$ ${\mathrm{H}}_3$, 154 173.25 for ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ ${\mathrm{D}}_3$, and 153 600.82 for ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$ ${\mathrm{D}}_3$. Structural dimensions for the ground vibrational state of ammonia obtained by isotopic substitution are 1.0136 Å for the bond length and 107°3' for the bond angle. For P${\mathrm{H}}_3$, the rotational constants obtained (in Mc/sec) are: $B_0=133\mathrm{} 480.15$, $D_J=3.95\mathrm{}$, and $D_{\mathrm{JK}}=-5.18\mathrm{}$; for P${\mathrm{D}}_3$ they are $B_0=69\mathrm{} 471.09$, $D_J=1.02\mathrm{}$, and $D_{\mathrm{JK}}=-1.31\mathrm{}$. An upper limit of ½ Mc has been put on the unknown inversion frequency of P${\mathrm{H}}_3$.