ENERGY PARTITIONING IN HYPERTHERMAL O++H2O CHARGE-TRANSFER COLLISIONS

The energy partitioning in hyperthermal O++H2O charge-transfer collisions is determined from the analysis of guided-ion beam time-of-flight measurements. The experimentally determined H2O+ laboratory velocity distributions exhibit a main band due to near-thermal ions and a weak channel due to center-of-mass backscattered ions. The velocity distributions are fit to simulated distributions based on an osculating complex model. The charge-transfer products formed via the shortest lived complexes exhibit little translational-to-internal energy transfer, resulting in internal energies of 1.0 +/- 0.2 eV. Contributions due to longer-lived complexes are observed and result in increased internal excitation. The internal energy distribution is, however, non-statistical because the lifetime of these complexes is considerably shorter than their rotational period.