ANALYSIS OF THE $D^{\prime} \rightarrow A^{\prime}$ TRANSITION IN THE EMISSION SPECTRUM OF $Cl_{2}$

Abstract

The emission spectrum of $Cl_{2}$ in Ar is re-examined using Tesla discharge sources containing isotopically pure $^{35}Cl_{2}$ and $^{37}Cl_{2}. ^{1}$ Earlier speculation that the dominant emission near $2580 {\AA}$ is due to the $D^{\prime}2g(^{3}P_{2}) \rightarrow A^{\prime} 2_{u}(^{3}\Pi$) transition is confirmed, with the following constants (in $cm^{-1}$) obtained for these states: $\Delta T_{e} = 40125.4, w_{e}^{\prime} = 253.17, w_{e}x_{e}^{\prime} = 1.14, w_{e}'' = 257.27, w_{e}x_{e}^{\prime\prime} = 4.86$. This same transition is also primarily responsible for the $long-known^{2}$ transient absorption spectrum of photoflashed $Cl_{2}$, which was previously interpreted in terms of absorption from the $B^{3}\Pi {O}+{u}$ state. The emission spectrum contains weaker contributions from a second band system, tentatively assigned as $B1_{g}(^{3}P_{2}) \rightarrow A 1_{u}(^{3}\Pi)$. A rotational analysis of $D^{\prime} \rightarrow A^{\prime}$ is now in progress and will be reported.