RADIATIVE LIFETIME OF CO-2-SIGMA(+),V) IONS((X)

The radiative relaxation of CO+(X-2 Sigma(+), nu) ions produced by ion ization of CO and of OCS with 70 eV electrons has been investigated us ing the monitor ion technique in a triple FT ICR spectrometer. Since t he monitor reaction is exothermic for nu greater than or equal to 1, t he experimental lifetimes, 170 ms for CO+ from CO and 210 ms for CO+ f rom OCS, should correspond to the overall decay rate of nu greater tha n or equal to 2 with a small contribution of nu=1. These values being much larger than the theoretical lifetime of nu=1 (128.5 ms), computer -simulated overall lifetimes for nu greater than or equal to 1 and nu greater than or equal to 2 have been determined using theoretical life times calculated by Rosmus and Werner and a vibrational population ded uced from photoelectron spectroscopy of CO with 40.8 eV photons (Gardn er and Samson). The computer-simulated lifetimes, 250 ms for nu greate r than or equal to 1 and 125 ms for nu greater than or equal to 2, are indeed about twice as large as the theoretical lifetimes for nu=1 and nu=2, respectively, indicating that the large experimental lifetimes may be accounted for by radiative cascade from the upper vibrational l evels. (C) 1998 Elsevier Science B.V.