Predissociation and spectroscopy of the ~3A _2(000) state of ~(18)O _3 from CRDS spectra of the ~3A _2(000)←X ~1A _1(110) hot band near 7900cm ~(-1)

摘要

The spectroscopy and predissociation of the ~3A _2(000) state of ~(18)O _3 are investigated from the analysis of the absorption spectrum of the ~3A _2(000)←X→1A1(110) hot band recorded by high sensitivity cw-CRDS between 7600 and 7920cm ~(-1). The noise equivalent absorption of the recordings is on the order of 1×10 ~(-10)cm ~(-1). Forty transitions could be rotationally assigned and their line positions were used to derive approximate spectroscopic parameters of the ~3A _2(000) upper state. Most of the transitions exhibit a clear broadening due to the predissociation of the ~3A _2(000) upper state at 9573.61cm ~(-1). The width of the Lorentzian component (from 0.02 up to more than 0.5cm ~(-1)) was retrieved for some of the assigned transitions. The variation of the corresponding predissociation rates is due to the dependence of the spin-orbit coupling between the ~3A _2(000) level and high lying dissociative vibrational levels of the X→1A1 electronic ground state, with (i) the J and K _a rotational quantum numbers and (ii) the energy gap between the coupled pair of rotational levels. From the predicted energies of the X→1A1 vibrational states and their vibrational overlap with the ~3A _2(000) state, a few of these X→1A1 vibrational levels are identified as possibly responsible for the ~3A _2(000) predissociation. The predissociative mechanism in ~(18)O _3 is compared to that taking place in ~(16)O _3.