Predissociation lifetimes of the A2Σ+ v = 1 state of the SH radical determined by cavity ring-down spectroscopy

The SH(A-X) (1,0) band has been investigated further, in absorption, using the technique of cavity ring-down spectroscopy. Careful lineshape measurements reveal the predissociation rate of these radicals to increase gradually with increasing rotational quantum number; the corresponding lifetimes decrease from 5.5 ± 0.2 ps (N′ = 0) to 4.6 ± 0.6 ps (N′ = 8). Such behaviour has been reproduced, quantitatively, by Fermiʹs Golden Rule calculations which employ the best available (experimentally determined) potential energy function fo the A2Σ+ state together with ab initio curves for the dissociative 14Σ− state and for the R dependence of the spin-orbit matrix element linking these two states.