Electron impact excitation of H2O

Abstract

Relative differential cross sections for elastic scattering and for a number of inelastic processes corresponding to vibrational and vibronic excitation of H2O have been determined at 53, 20, and 15 eV impact energies in the 0°–90° angular range. The measurements were carried out with an instrumental resolution of about 80 meV for transitions corresponding to the following energy losses: 0.45 eV(nu1 and/or nu3); 0.90 eV (nu1+nu3); 4.5 eV [tripletstate(s)]; 7.4 eV (Ã1B1); 9.7 eV (B-tilde1A1); 9.81 eV (tripletstate); 10.00 eV [C-tilde1B1 (0,0,0)]; 10.17 eV [D-tilde1A1 (0,0,0)]; 10.38 eV [C-tilde1B1 (1,0,0)]; 10.57 eV [D-tilde1A1 (1,0,0)]; 10.76 eV [C-tilde1B1 (2,0,0)] and [D-tilde1A1 (1,1,0)]; 11.01 eV (E-tilde1B1); and 11.11 eV (F-tilde). On the basis of the angular distribution of the scattered electrons, it is suggested that the 4.5 and 9.81 eV transitions are associated with excitations of triplet states, while the angular distribution of the scattered electrons at all other energy losses indicate predominantly singlet-singlet transitions. The sharpness of the 9.81 eV transition indicates that the corresponding state has an equilibrium geometry similar to that of the ground state.