Excimer emission band at 235.5 nm in the XeCl molecule

Band emission at 235.5 nm is observed in fast discharge in a Xe/Cl2 mixture at low pressure. This emission has the same spectral width as that of the excimer 2Σ+1/2→ 2Σ+1/2 transition at 307 nm. It is suggested that this band is also due to bound-free transitions, but belongs to the spin-orbit split level 2Π state of the ionic XeCl molecule that correlates with Xe+(2P1/2) and Cl−(1S). The molecular energy gap between 2Σ+1/2 and 2Π1/2 is almost equal to the atomic spin-orbit splitting and their potential curves are very similar. This bound-free 2Π1/2→2Σ+1/2 emission may be an excimer laser candidate.