RADIATIVE LIFETIMES FOR AN ION OF ASTROPHYSICAL INTEREST - HCO+

Radiative lifetimes for vibrationally excited ground state HCO+ ions h ave been determined in a triple-cell FT-ICR spectrometer using the pro ton transfer reactions with HBr, N2O, HCl, CH4, CO2 and NO to probe th e time evolution of HCO+ internal energy. With HBr, N2O, HCl and CH4 t wo sets of lifetimes are obtained; the long ones (359-50 ms) are assig ned to the bending mode levels, and the short ones (10-30 ms) to the C H and CO stretching modes. Correction of the observed lifetimes for co llisional quenching is discussed in detail. A simple model has been us ed to simulate the influence of the radiative cascade. The experimenta l lifetimes obtained for the bending mode levels are in good agreement with the simulated lifetimes. For the fast components the experimenta l uncertainty is too large to allow any conclusion to be drawn about t he lifetime of the individual stretching modes.