CHARGE-TRANSFER DYNAMICS IN ION-POLYATOMIC MOLECULE COLLISIONS - X(+)+H2O (X=N,KR) LUMINESCENCE STUDY

H2O+ (A) over tilde (2)A(1)-(X) over tilde B-2(1) luminescence spectra are presented for the X(+)+H2O (X=N,Kr) charge-transfer systems at co llision energies ranging between 0.4 and 130 eV (c.m.). The luminescen ce is attributed to bending vibrational states near-resonant with N+(P -3)+H2O and Kr+(P-2(1/2))+H2O reactants, in agreement with energy reso nance and Franck-Condon predictions. H2O+ (A) over tilde-state product vibrational distributions are obtained from spectral simulations. The energy dependence of vibrational state-to-state cross sections is det ermined for the N+(P-3)+H2O charge-transfer system, where the integral charge-transfer cross section is known. The cross sections are relate d to semiclassical charge-transfer models. Exothermic product states a re interpreted to be primarily governed by curve crossings along the b ending coordinate of H2O, while endothermic levels can be rationalized using a Demkov-type mechanism. The Kr+(P-2(1/2))+H2O luminescence stu dy, for which state-selected cross sections are not available, provide s product state distributions consistent with this interpretation. The higher optical resolution in that experiment, however, enables a K-su bstate resolved analysis, as well as an approximate assessment of the product rotational temperature. The observed rotational temperatures a re near thermal, implying long-range processes governed by large impac t parameters. (C) 1995 American Institute of Physics.