Compensation for non‐normal ejection of large molecular ions in plasma‐desorption mass spectrometry

By introducing an Einzel lens in the field‐free region of a straight time‐of‐flight mass spectrometer, secondary ions of large mass can be detected more efficiently in plasma‐desorption mass spectrometry. This procedure compensates for the large radial velocities of large molecular ions recently observed experimentally. It is shown that large molecular ions like those of lysozyme can now be detected more efficiently, and larger molecular ions than observed before in plasma‐desorption mass spectrometry (like those of bovine ovalbumin, mol. wt 45 000) can now be studied.