The UV absorption of ClO - Part 1. The A(2)Pi-X-2 Pi spectrum at wavelengths from 285-320 nm studied by cavity ring-down spectroscopy

The UV absorption of ClO at wavelengths between 285 and 320 nm has been inv estigated using cavity ring-down spectroscopy. This wavelength region spans the (0,0) to (7,0) bands of the A (2)Pi(3/2)-X (2)Pi(3/2) and A (2)Pi(1/2) -X (2)Pi(1/2) transitions. The previously unobserved A (2)Pi(3/2)-X (2)Pi(3 /2) (0,0) and (1,0) absorption bands have been recorded with rotational res olution, and spectra of the (2,0) to (6,0) bands of the A (2)Pi(1/2)-X (2)P i(1/2) transition are shown for the first time. Analysis of the spectra giv es refined band origins and rotational constants for the A (2)Pi upsilon' l evels and reveals a strong upsilon' dependence in the linewidths of rotatio nal features. The lifetimes of the A (2)Pi(3/2) upsilon' = 0-2 and A (2)Pi( 1/2) upsilon' = 2-4 levels are revised from previous estimates, and the lif etimes of A (2)Pi(1/2) upsilon' = 5 and 6 levels have been determined. The deduced predissociation rates for A (2)Pi(3/2) upsilon' = 3-7 confirm earli er studies. The lifetimes of vibrational levels of the two spin-orbit compo nents of the A (2)Pi(Omega) state are markedly different. No evidence of J' -dependence in the predissociation is found, in contrast to the correspondi ng A (2)Pi(3/2) state of the IO radical.