Absorption spectroscopy of the plasma of a He/Sr discharge laser: panoramic absorption spectrum in the visible range

A panoramic absorption spectrum of the plasma of a He/Sr laser at the time of the maximum discharge current has been measured by time-resolved absorption spectroscopy. The spectral resolution was no worse than 0.003 nm. Anomalously broad bands (about 0.5 nm wide) are found in the interval 613–645 nm. The absorption kinetics in these bands is correlated most closely with, for example, the population kinetics of the 4²F_7/2 state of the strontium ion. It is suggested that the most probable source of these bands is an absorption accompanying bound-free (or free-bound) transitions of (HeSr⁺)* or (SrSr⁺)* molecular ions or HeSr excimer molecules. The absorption kinetics of certain states of He*, Sr, Sr*, Sr⁺, and Sr⁺* is also described in qualitative terms.