Knowledge Bank

The emission spectrum of the $A\prime \mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi (2)-X1\Sigma g+$ system of $Br2$ in an argon matrix is reported. This spectrum has been vibrationally analysed for the first time, and the analysis supports two possible vibrational numberings. These provide estimates for $Te$ of $12966\pm 8cm-1$ and $12679\pm 8cm-1$ respectively. Excitation spectra have been recorded for the A-X and $A\prime -X$ systems in the region of 490-540 nm. The observed profiles are consistent with direct absorption into the A state continuum. This is at variance with a previous interpretation which indicated that absorption at these wavelengths leads initially to population of the B state, followed by rapid relaxation into the A and $A\prime$ $states.1$ Further details of the excitation mechanism are being sought in photoselection studies, and the results of these experiments will be presented.