Radial velocities of ejected ions: implications for the mechanisms of molecular ion formation in plasma desorption mass spectrometry of biomolecules

Abstract

Experimental data are presented on the initial radial velocity distributions of different types of secondary molecular ions, M + , [M + H] + and [M + Na] +, ejected from biomolecular samples. An incident beam of 48 MeV 127I 11 + ions was employed to generate the secondary ions. Measurements were carried out in a reflectron time-of-flight mass spectrometer by monitoring the secondary ion yield as a function of electrostatic deflection in a direction perpendicular to the target surface normal. The data are interpreted in terms of current models describing the ejection process in plasma desorption mass spectrometry.