Bromine excited, from photolysis

Fig. 9. Electronically excited bromine atoms, Br(42Pyt), resulting from the flash photolysis of IBr. Pibt = 0.03 mm Hg, pAr = 100 mm Hg, E = 780 J.

Schrock and Schuster [46] have demonstrated that the quantum yield to loss of nitrogen from triplet phenyl azide is rather low. The fact that a strong transient spectrum of the brominated triplet phenyl nitrene is observed following laser flash photolysis thereby implies that the heavy atom effect has catalyzed intersystem crossing from the singlet to the triplet state of the nitrene rather than of the azide excited state. 

---