Perturbations in the Ultraviolet Band Spectrum ofP2

The emission spectrum of the ultraviolet band system of ${\mathrm{P}}_2$ has been photographed in the third and fourth orders of a 21-ft concave grating. Strong rotational perturbations were found in the $v^{\prime }=5, 7, 8, \mathrm{and} 9$ vibrational levels of the upper electronic state. These perturbations were fully determined. It is shown that the vibrational perturbations of the bands which result from the $v^{\prime }=5\mathrm{}$ level are caused by the rotational perturbations in this level. The following values were obtained for the equilibrium constants: