Uncoupling Effects in the Microwave Spectrum of Nitric Oxide

The results obtained from the microwave measurements of the rotational spectra of ${\mathrm{N}}^{15}$ ${\mathrm{O}}^{16}$ and ${\mathrm{N}}^{14}$ ${\mathrm{O}}^{16}$ in their ${}_{}{}^2{}_{}{}^{}\Pi _{\frac{1}{2}}^{}{}_{}{}^{}$ ground state are compared by isotopic substitutions and shown to be in excellent agreement. The NO molecule is considered as an intermediate case, slightly removed from Hund's case (a). The theory of spin uncoupling and $l$ uncoupling, developed by Van Vleck and extended by Dousmanis, Sanders, and Townes, is applied to the two molecules, and the molecular parameters are calculated accordingly. The resulting rotational constants are $B_0=49\mathrm{}041.34$ Mc/sec and $D_0=0.139\mathrm{}$ Mc/sec for ${\mathrm{N}}^{15}$ ${\mathrm{O}}^{16}$, and $B_0=50\mathrm{}838.56$ Mc/sec and $D_0=0.177\mathrm{}$ Mc/sec for ${\mathrm{N}}^{14}$ ${\mathrm{O}}^{16}$. The A-doubling constants are found to have the following values: $p_{\Lambda }=170.45\mathrm{}$ Mc/sec for ${\mathrm{N}}^{15}$ ${\mathrm{O}}^{16}$ and 176.15 Mc/sec for ${\mathrm{N}}^{14}$ ${\mathrm{O}}^{16}$; and $q_{\Lambda }=0.71\mathrm{}$ Mc/sec for ${\mathrm{N}}^{15}$ ${\mathrm{O}}^{16}$ and 1.15 Mc/sec for ${\mathrm{N}}^{14}$ ${\mathrm{O}}^{16}$.