The UV absorption of ClO Part 1. The A2Π–X2Π spectrum at wavelengths from 285–320 nm studied by cavity ring-down spectroscopy

Abstract

The UV absorption of ClO at wavelengths between 285 and 320 nm has been investigated using cavity ring-down spectroscopy. This wavelength region spans the (0,0) to (7,0) bands of the A²Π_3/2–X²Π_3/2 and A²Π_1/2–X²Π_1/2 transitions. The previously unobserved A²Π_3/2–X²Π_3/2 (0,0) and (1,0) absorption bands have been recorded with rotational resolution, and spectra of the (2,0) to (6,0) bands of the A²Π_1/2–X²Π_1/2 transition are shown for the first time. Analysis of the spectra gives refined band origins and rotational constants for the A²Π v′ levels and reveals a strong v′ dependence in the linewidths of rotational features. The lifetimes of the A²Π_3/2v′=0–2 and A²Π_1/2v′=2–4 levels are revised from previous estimates, and the lifetimes of A²Π_1/2v′=5 and 6 levels have been determined. The deduced predissociation rates for A²Π_3/2v′=3–7 confirm earlier studies. The lifetimes of vibrational levels of the two spin–orbit components of the A²Π_Ω state are markedly different. No evidence of J′-dependence in the predissociation is found, in contrast to the corresponding A²Π_3/2 state of the IO radical.