| 摘要 |
The invention relates to the generation of daughter ion spectra from analyte substances that are ionised by matrix assisted laser desorption. The invention consists in reflecting the ion beam 9 in at least one electrical reflector 18 prior to a parent ion selector 10 in order to mask out all those ions that have a false kinetic energy, so that only ions that have both the mass of the parent ions and their kinetic energy are allowed to pass the parent ion selector 10; parent ions with dispersed initial energies are actually focused on the parent ion selector 10 with improved timing. By taking this measure, the mass resolution and improved signal to noise ratio produce higher sensitivity even though fewer ions are admitted for analysis in the daughter ion spectrum. The electrical reflector 18 is combined with a further reflector 19 and/or a plurality of deflection capacitors (43 and 44 in Figs 5 and 7) so that the ion beam 9 returns to its original direction. |
