Submillimeter-Wave Spectra of Ammonia and Phosphine

Abstract

Rotational transitions of different isotopic species of ammonia and phosphine have been observed in the \textonehalf{}- to 1-mm region. The frequency of the $J=0\ensuremath{\rightarrow}1$ transition of $^{14}\mathrm{N}$${\mathrm{H}}_{3}$ is 572 496.69 \ifmmode\pm\else\textpm\fi{} 0.60 Mc/sec and that for $^{15}\mathrm{N}$${\mathrm{H}}_{3}$ is 572 053.18 \ifmmode\pm\else\textpm\fi{} 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}$. Structural dimensions for the ground vibrational state of ammonia obtained by isotopic substitution are 1.0136 \AA{} for the bond length and 107\ifmmode^\circ\else\textdegree\fi{}3' for the bond angle. For P${\mathrm{H}}_{3}$, the rotational constants obtained (in Mc/sec) are: ${B}_{0}=133 480.15$, ${D}_{J}=3.95$, and ${D}_{\mathrm{JK}}=\ensuremath{-}5.18$; for P${\mathrm{D}}_{3}$ they are ${B}_{0}=69 471.09$, ${D}_{J}=1.02$, and ${D}_{\mathrm{JK}}=\ensuremath{-}1.31$. An upper limit of \textonehalf{} Mc has been put on the unknown inversion frequency of P${\mathrm{H}}_{3}$.