New predissociations of the A state in SiH and their use in deriving an improved value of the dissociation energy

An exhaustive high-resolution study of the lifetimes of the A 2 Delta state of SiH has been made for a number of rotational levels of the v'=0, 1 and 2 progressions using the high-frequency deflection technique. From these results, together with a close comparison of similar results on the analogous A 2 Delta state in CH, evidence is given for predissociation following direct vibrational coupling with the X 2 Pi ground state, and the dissociation energy for SiH is determined as D 0 o =26950+or-200 cm -1 . In addition, the lifetime values have been used, together with Franck-Condon factors to establish a small variation of the transition moment, and the absorption oscillator strength for the A-X (0,0) band is determined as f(0,0)=(4.98+or-0.15)*10 -3 .