Abstract
Transient absorption in the 450 to 650 nm spectral region has been observed in the discharge channel of a UV pre-ionised mercury bromide laser. To the red side of the HgBr(B-X) gain region, continuum absorption due to the X-A transition in HgBr, and atomic mercury absorption at 546 nm are seen. The X-A continuum is found to be blue shifted by 0.3 eV relative to theoretical predictions, and to overlap the 502-504 nm laser emission region. On the blue side of the gain band, absorption due to the X-B transition and absorption by the B state to higher energy HgBr states are identified through their differing time dependencies. Immediately following the discharge, the HgBr concentration falls rapidly, with a half-life of 1 mu s, through chemical reactions producing molecular bromine. This short lifetime may be a limitation on the optically pumped HgBr laser using UV excitation of the X-B band.

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