Rotational Structure of the Red Bands of Potassium

Abstract

A rotational analysis has been made of four bands of the red system of ${\mathrm{K}}_2$ which had been photographed under high dispersion. The principal molecular constants of the ground state (${}_{}{}^1{}_{}{}^{}{\Sigma }_g_{}^{+}{}_{}{}^{}$) and of the upper state (${}_{}{}^1{}_{}{}^{}\Pi _u^{}{}_{}{}^{}$) are as follows: $\left\{\right\}\{ {B_0}^{\prime \prime }=0.05611\mathrm{} {r_e}^{\prime \prime }=3.91\mathrm{}\times {10}^{-8\mathrm{}} {\alpha }^{\prime \prime }=0.000219\mathrm{}\}\{{B_0}^{\prime }=0.04812\mathrm{} {r_e}^{\prime } =4.22\mathrm{}\times {10}^{-8\mathrm{}} {\alpha }^{\prime } =0.000235\mathrm{}\}$ The magnitude of the $\Lambda$ type doublings of the ${}_{}{}^1{}_{}{}^{}\mathrm{II}$ state agrees with Van Vleck's formula for it. The relationships between the molecular constants show that all rotational levels, with both even and odd values of $J$, are present. Alternating intensities are observed, the lines with odd $J^{\prime \prime }$ being stronger. It is concluded that the nuclear spin of $K^{39}$ is definitely not zero, and that the nucleus obeys the Fermi-Dirac statistics.