Nature of the wide-band absorption in the plasma of the He/Sr laser

The wide (~0.5-nm) bands which have been observed previously in the red part of the absorption spectrum of the plasma of a pulsed electric-discharge He/Sr laser are shown to result from transitions to autoionization states of the strontium atom. They are completely unrelated to molecular (or ionic-molecular) absorption. Quantitative measurements of the spectral width and relative strength of the observed transitions are reported. These transitions are identified.