Collisional ionization of highly excited Rydberg states of polyatomic molecules

Abstract

The ionization has been observed for most of the nine polar and three nonpolar organic molecules studied, and kinetic parameters have been evaluated for acetone, acetaldehyde-H₄ and -D₄ methyl bromide and ethylene-D₄ at excitation energies E in the range 0.01-0.08 eV below the ionization potential I. Also, the ratio k₂/k₂' of the rate constant for collisional ionization for collisions of the excited molecules with ground-state molecules to that for collisions with additive gas molecules has been evaluated for the binary mixtures of CH₃COCH₃+He, Ne, Ar or N₂, CH₃CHO+He, CD₃CDO+He, CH₃Br+He or Ar and C₂D₄+Ar. The k₂/k₂' values range from 20 to more than about 3000, with values not less than 800 for most of the mixtures with polar molecules and I-E2 for the polar molecules and with the unimolecular decay rate constant being determined by the predissociation rate. Also, the mechanism of collisional ionization is discussed briefly.