FRAGMENTATION OF THE OVER-TILDEC(2)T(2) AND OVER-TILDED(2)A(1) STATESOF CCL4-PHOTOION COINCIDENCE SPECTROSCOPY( AND SICL4+ STUDIED BY THRESHOLD PHOTOELECTRON)

Threshold photoelectron-photoion coincidence (TPEPICO) spectroscopy ha s been used to study the decay pathways of the ($) over tilde C T-2(2) and ($) over tilde D (2)A(1) excited electronic states of CCl4+ and S iCl4+ in the range 14-23 eV. Vacuum UV photons from a synchrotron radi ation source ionise the parent neutral molecule, and the electrons and ions are detected by threshold electron analysis and time-of-flight m ass spectrometry, respectively. TPEPICO spectra are recorded continuou sly as a function of photon energy, allowing ion yield curves to be ob tained. The ($) over tilde C and ($) over tilde D states of CCl4+ frag ment exclusively to CCl2+ and CCl+ respectively, corresponding to non- statistical routes. Radiative decay from the ($) over tilde C state of SiCl4+ is an important process and this state fragments indirectly to SiCl3+ by fluorescence from the ($) over tilde C state, followed by d issociation from lower-lying repulsive states. The ($) over tilde D st ate of SiCl4+ fragments exclusively to SiCl2+. Kinetic energy releases into CCl2+ + Cl-2 and SiCl3+ + Cl have been measured at the Franck-Co ndon maximum of the ($) over tilde C T-2(2) states of the two parent i ons.