Variation with Temperature of the Continuous Absorption Spectrum of Diatomic Molecules: Part II. Theoretical

Abstract

A method of calculating the matrix components, corresponding to the continuous absorption of light by diatomic molecules in various vibrational and rotational levels of the lower state, is described and applied to the calculation of the absorption of ${\mathrm{Cl}}_2$ gas at various temperatures. The theory shows that the absorption from a single vibrational level is practically independent of temperature, and that the temperature effect is due to the changing distribution of the absorbing molecules among the various levels. Assuming the Morse function to be approximately correct for the potential energy of the lower state, the theory enables one to calculate the form of the upper potential energy curve. The matrix component of the electric moment corresponding to the absorption from the lower state has been calculated for ${\mathrm{Cl}}_2$ and found to correspond to the displacement of one electronic charge through 0.016A.