Studies of Ionization Efficiency. Part III. The Detection and Interpretation of Fine Structure

Abstract

The effect of the spread in energy of the ionizing electron beam on the resolution of structural details in ionization efficiency curves has been evaluated, and the possibility of its removal by analytical methods is discussed. It has been shown that the first and second derivatives of the ionization efficiency possess useful properties, and that, when certain assumptions are made about the shape of the ionization probability function for a single process, a new method of measuring ionization potentials can be devised. Correlation techniques have been employed to enhance materially the signal-to-noise ratio in the output from the ion collector. Detailed measurements of the ionization efficiencies for the inert gases have been made, and the assumptions referred to are justified. It is shown that the ionization efficiencies for some molecular ions can be correlated with their vacuum ultraviolet and near x-ray spectra. It is found that competition occurs between all possible processes of excitation and ionization at each level of energy. The higher-energy levels of molecules can be studied and, in principle, an unequivocal assignment of bond dissociation energies from mass spectrometric data is possible.