Knowledge Bank

The $A\prime$ state of $I2$ was obsereved for the first time in a free-jet expansion, where it was prepared by ArF laser excitation of $I2$/Ar mixtures close to the $nozzle1$. Twenty seven bands in the v"" = 0 progression of the $D\prime -A\prime$ transition were studied by laser excitation spectroscopy, leading to the following improved constants $(cm-1)$ for the $A\prime andD\prime$ states: \begin {eqnarray*}B_{0}^{-} = 0.028054, Be^{\prime} = 0.020526, \alpha_{e}^{\prime} = 5.3 \times 10^{-5},\ \omega_{e}^{\prime} = 103.953, \omega_{e}x_{e}^{\prime} = 0.2097, \omega_{e}y_{e} = 2.687 \times 10^{-4}\end {eqnarray*}. Many bands of the $\beta -A$ transition have also been observed. These originate from A, $v-=0$, and terminate on levels with $25\le v\prime \le 68$ of the $\beta$ state. Full analyses of both band systems will be presented.