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

Excitation functions for both positive and negative ions (X+ + Y-), fo rmed by photodissociation in the vicinity of the onset of molecular io nization, for the jet-cooled interhalogen systems BrCl, ICl and IBr ar e reported. The overall shape of the excitation functions indicates th at a number of overlapping Rydberg systems are accessed leading to dis sociation. From analyses of the ion-pair excitation functions of the t hree molecules, by means of simulation calculations, the dominant Rydb erg 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 (2 PI1/2)(c)nssigma are also found to be present. It is concluded that th e formation of ion pairs occurs by the same process in all three inter halogens, i.e. via predissociation of bound Rydberg states by ion-pair states.