DETAILED STUDY OF THE EFFECT OF INSTRUMENTAL PARAMETERS ON THE SHAPE OF A MIKE PEAK

The shapes of ion kinetic energy peaks are used to estimate translational energy releases during fragmentation reactions of ions. It is shown that these shapes are extremely sensitive to particular instrumental parameters and that, if special precautions are not taken in setting up the instrument, the detailed peak shapes and the widths of the peaks at half-height will depend upon the inaccuracies in the setting-up procedure. In particular, the lengths of all slits are important; the shorter the slits the more accurate the distribution of energies that can be obtained. Good angular collimation is also important and one must ensure that no inadvertent deflections of the beam occur in the direction parallel to the slit lengths. Drift of the magnet current must also be prevented, preferably by the use of a beam-locking system. Methods for investigating the above are described and their effects on peak shapes are illustrated. © 1979.