Laser-induced fluorescence studies of water by electron impact.

Using a magnetically collimated electron beam crossed with a jet-cooled molecular beam, the break-up of water into slow ground state OH radicals has been probed using Laser Induced Fluorescence (LIF). Particular attention is given to the near threshold region where the relative cross sections for the production of OH(A, v = 0) and OH(X, v = 0) are obtained and compared to each other. The similarity between the shapes and appearance energies of the two cross sections allow us to conclude that production of the OH(A) and OH(X) states are closely related. The fact that little evidence is obtained for H2O break up into fast OH(X) fragments, strongly suggests that exchange excitation producing slow fragments is much more effective than dipole allowed processes, which will produce predominantly fast fragments. The rotational temperature of OH(X) was determined to be about 210K using the P and R lines and 270K using the Q lines. A Λ-doublet population inversion was found to exist within the OH ground state. The pi-/pi + population ratio was 1.9 for all observed lines. Also we were able to observe preferential population of the 2pi3/2 spin state over the 2pi1/2 state by a factor of 1.65. The LIF signal was also found to be dependent on the laser polarization with respect to the electron-laser plane. The value obtained, 1.1 +/- 0.3, agrees within statistical error with the expected result.Dept. of Physics. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1998 .H365. Source: Masters Abstracts International, Volume: 39-02, page: 0521. Adviser: J. W. McConkey. Thesis (M.Sc.)--University of Windsor (Canada), 1998.