Submillimeter Wave Spectroscopy: Rotation-Inversion Transitions in ND3

The $J=0\mathrm{}\to 1$ rotational transition of ${\mathrm{N}}^{14}$ ${\mathrm{D}}_3$ has been measured at a wavelength of 0.97 mm. This transition is split into two components by inversion doubling of the ground vibrational levels. The frequencies of the two components were found to be 306 735.0 Mc/sec and 309 909.35 Mc/sec. Their separation, 3174.4 Mc/sec, is equivalent to the sum of the inversion frequencies of the upper and lower states. The relative intensities of the upper and lower frequency components were found to be about 10 to 1, in agreement with theory. The $B_0$ value, 154 162.7 Mc/sec, is obtained from the arithmetic mean of the two components, with the infrared value, $D_J=3.4\mathrm{}$ Mc/sec. The $B_0$ value is consistent with a bond length of 1.0144 A and a bond angle of 107°. Superimposed upon each of the inversion components is a triplet hyperfine structure caused by the ${\mathrm{N}}^{14}$ quadrupole moment. This structure was measured for the higher frequency component, and the value, $eQq=-4.20\mathrm{}\pm 0.15$ Mc/sec, was obtained for the ${\mathrm{N}}^{14}$ coupling.