Molecular-Beam Maser for the Shorter-Millimeter-Wave Region: Spectral Constants of HCN and DCN

A millimeter-wave molecular-beam maser has been made to operate as both an amplifier and an oscillator on the $J=1\mathrm{}\to 0$ and the $J=2\mathrm{}\to 1$ transitions of HCN at 88.6 and at 177.2 kMc/sec, respectively, thus doubling the previously operational frequency range of such masers. With this maser, hyperfine components of these transitions have been measured for ${\mathrm{H}}^{12}$ ${\mathrm{C}}^{14}$N and ${\mathrm{D}}^{12}$ ${\mathrm{C}}^{14}$N to nine significant figures. The spectral constants (in kc/sec) that are derived from these frequencies are, for HCN, $B_0=44\mathrm{}315975.7\pm 0.4$, $D_J=87.24\mathrm{}\pm 0.06$, ${\mathrm{}\left(\mathrm{eQq}\right)\mathrm{}}_N=-4709.1\mathrm{}\pm 1.3$, and $C_{\mathrm{N}}=10.4\mathrm{}\pm 0.3$; for ${\mathrm{D}}^{12}$ ${\mathrm{C}}^{14}$N, $B_0=36\mathrm{}207462.7\pm 0.2$, $D_J=57.83\mathrm{}\pm 0.04$, ${\mathrm{}\left(\mathrm{eQq}\right)\mathrm{}}_{\mathrm{N}}=-4703.0\mathrm{}\pm 1.2$, $C_{\mathrm{N}}=8.4\mathrm{}\pm 0.3$, ${\mathrm{}\left(\mathrm{eQq}\right)\mathrm{}}_{\mathrm{D}}=194.4\mathrm{}\pm 2.2$, and $C_{\mathrm{D}}=-0.6\mathrm{}\pm 0.3$.