Atomic Absorption Coefficients and Transition Probabilities

Abstract

THREE recent letters raise the question as to whether there is any experimental basis for applying Kramers' equation for continuous absorption to astrophysical problems¹. Ditchburn cites the anomalous phenomena shown by alkalis at the absorption series limits as the only direct experimental evidence. A series of papers² by me on the emission spectra of cæsium vapour gives direct evidence as to the transition probabilities for the continuous spectra and line spectra of the levels 6 P and 5 D. The first paper indicated that the probability of recombination depended on the pressure but subsequent work showed this to be erroneous, and the last paper (published after the appearance of Ditch-burn's letter) shows that the continuous transition probabilities remain nearly constant with electron concentrations ranging from 10¹² to 10¹⁶ per cm.³ and with pressures from 0.001 mm. to 17 mm. of mercury.