Influence of surface charge field on the electron impact fragmentation pattern of KCl molecules in the free surface vaporization of single crystals

Abstract

A mass-spectrometric method was used to investigate the temperature dependence of the electron impact fragmentation pattern of KCl molecules [ion current ratio I(K +)/ I(KCl +)] vaporizing from a free surface of a potassium chloride single crystal. In the temperature range 766–945 K a very good correlation is observed between the variation in fragmentation pattern with temperature and the pattern of the curve E versus T, where E is the strength of surface charge field. It is concluded that molecules desorbing from an open crystal surface may possess excessive vibrational and rotational energy compared to that characteristic of thermal excitation.