Time resolved study of the luminescence produced by the pulse radiolysis of D2O vapor

Abstract

D2O vapor was irradiated using a 0.53 MeV pulsed electron beam and the 200–900 nm wavelength range was examined for luminescence emission from excited fragments. Spectral lines of the OD (C 2∑+→A 2∑+) and the OD (A 2∑+→X 2Π) transitions were observed, as were the Balmer transitions of deuterium between n=6→n=2 and n=3→n=2, and the oxygen transitions O+(3p 4D0→3s 4P),O(3p 5P→3s 5S0), and O(3p 3P→3s 3S0). Values were obtained for the natural lifetimes, quenching rate constants, and quenching cross sections at 298 K for the majority of the above excited species. The natural lifetimes and quenching data obtained for the transitions of excited OD and oxygen species were, as expected, similar to the values obtained for the corresponding species in H2O vapor. However, Balmer D transitions exhibited shorter natural lifetimes and smaller quenching cross sections than the corresponding Balmer H transitions. The differences in quenching rate were much larger than the effect of isotopic substitution on collision frequency. Both lifetime and quenching differences were attributed to greater population of the p sublevels in excited D as compared with H.