Negative ion adsorption by the ion source surface as a factor influencing ion lifetime measurements

It is well known that negative ions formed in the gas phase through low-energy electron capture by molecules show a scatter in the measured lifetimes of their autodetachment states. In considering this question, it was found that, when using a static sector magnetic mass spectrometer, some of the ions formed on the ionization chamber walls are adsorbed and stabilized there, then joining the registered ion flux and thereby distorting their measured lifetime. Because the number of the adsorbed ions depends on the experimental conditions, their contribution to the total flux is to some extent uncontrollable—hence, the scatter. (instruments and methods of investigation)