ION-PAIR (X++Y-) FORMATION FROM PHOTODISSOCIATION OF THE INTERHALOGEN MOLECULES BRCL, ICL AND IBR

Excitation functions for both positive and negative ions (X+ + Y-), formed by photodissociation in the vicinity of the onset of molecular ionization, for the jet-cooled interhalogen systems BrCl, ICl and IBr are reported. The overall shape of the excitation functions indicates that a number of overlapping Rydberg systems are accessed leading to dissociation. From analyses of the ion-pair excitation functions of the three molecules, by means of simulation calculations, the dominant Rydberg systems involved are found to be X(2PI3/2)(c)nssigma and X(2PI1/2)(c)nssigma: other weaker Rydberg systems, with configurations X(2PI3/2)(c)nppi, A(2PI3/2)(c)nppi, A(2PI12)nppi, A(2PI3/2)(c)nssigma and A (2PI1/2)(c)nssigma are also found to be present. It is concluded that the formation of ion pairs occurs by the same process in all three interhalogens, i.e. via predissociation of bound Rydberg states by ion-pair states.