Measurement of "optical" transition probabilities of Cd

Of 31 level combinations in the cadmium atom the probability of spontaneous transition was found with the aid of the spectrum of an arc discharge between carbon electrodes in air with Cd vapour. For that purpose the intensities of the Cd lines were measured on the one side, while on the other side the populations of the upper levels of those lines were calculated from the simultaneously measured arc temperature. The temperature was derived from intensity ratios in the CN bands also occurring in the arc spectrum. The measurements are only relative; since, however, of one line the absolute value of the transition probability was known by other methods the relative results could be converted into absolute values. The results are summarized in table I. Checking measurements showed the absence of disturbing self-absorption etc., and confirmed the validity of Boltzmann's formula for the level populations in the used d.c. and a.c. arcs