Étude de l’interaction électron-molécule : transitions électroniques induites lors du choc

Institut de Chimie de l’Université de Liège, Belgique et Centre de Mécanique Ondulatoire Appliquée, 155, rue de Sèvres, Paris, 15 e, France.

Abstract

The transition probabilities from the ground state of an isolated molecule to electronically excited states of the corresponding monopositive ion when the molecule is submitted to a bombardment of monoenergetic electrons are discussed. These transition probabilities are shown to be related to the ionization cross section. An empirical relation expressing the dependence of the latter quantities on the energy of the electronic transitions and on the acceleration voltage of the impinging electrons is then proposed.

It is concluded that for a given energy of the bombarding electrons, the transition probability decreases regularly when levels more and more excited are considered. Transitions requiring 30 ev. and more, occur to a negligible extent, however energetic the impinging electrons may be.

The mass spectra of small molecules (N₂, O₂, NO, CO, CO₂ and H₂O) are calculated by means of these relations, and a satisfactory agreement with experiment is found.