The Infra-Red Spectrum and Molecular Constants of Nitric Oxide

The infra-red spectrum of nitric oxide has been remeasured under high dispersion with the result that the fundamental at 5.3μ has been almost completely resolved. The absorption in this region comprises two superposed bands arising from a ${}_{}{}^2{}_{}{}^{}\Pi _{\frac{1}{2}, \frac{3}{2}}^{}{}_{}{}^{}$ electronic ground state. In the $P$, and $R$ branches a great many of the lines split up into doublets, the components of which belong to these two bands, respectively. The lines were found to fit the following two empirical formulas: ${\nu }_{\Omega =\frac{1}{2}}=1877.36+3.34\mathrm{} J-0.019\mathrm{} J^2 {\mathrm{cm}}^{-1\mathrm{}}\mathrm{where} J=0,\pm \frac{3}{2},\frac{5}{2},\cdots ,$ ${\nu }_{\Omega =\frac{3}{2}}=1877.00+3.42\mathrm{} J-0.019\mathrm{} J^2 {\mathrm{cm}}^{-1\mathrm{}}\mathrm{where} J=0,\pm \frac{5}{2},\frac{7}{2},\cdots .$ An experimental curve in percent absorption against frequency in ${\mathrm{cm}}^{-1\mathrm{}}$ is compared with a theoretical intensity plot of the bands. From the new data some of the constants have been re-calculated, and compared with the results of the electronic band spectra. $I_0=1.63\mathrm{}\times {10}^{-39\mathrm{}}$ g ${\mathrm{cm}}^2$, $r_0=1.15\mathrm{}\times {10}^{-8\mathrm{}}$ cm, ${\nu }_0=1891.3\mathrm{}$ ${\mathrm{cm}}^{-1\mathrm{}}$.