A mechanism of Br2 formation in Ar/Br2 laser systems

The reaction of electronically excited state Br* (4p4, 5s) atoms with Br2 and BrI produces electronically excited Br*2, which gives a complex emission system in the 190–350-nm region. In both cases the excitation reaction probably involves bromine atom transfer with formation of Br*2. Similar reactions may be expected between other excited np4(n+1) s halogen atoms and suitable halogen donor molecules. These experiments were done in a flowing-afterglow apparatus at 1–8 Torr; the Br* atoms were generated from interaction of the precursor molecules with metastable argon atoms or with metastable helium atoms. Under high-pressure excitation conditions, formation of Br*2 by reaction of Br* with Br2 followed by vibrational relaxation may contribute to the excitation mechanism for the Br*2 laser system initiated by e-beam or discharge pumping of Br2/Ar mixtures.