A mass spectrometer for neutral sputtered atoms which are ionized with laser

摘要

An ion beam is impinged against a solid sample to sputter neutrals. The neutrals thus sputtered are ionized by a UV laser beam to obtain photoions. The photoions are guided to a quadrupole mass analyzer through an ion extraction electrode to extract ions having a desired mass. The extracted ions are made incident upon an ion detector to derive ion pulses. The number of ion pulses is counted by a counter through a signal gate which is opened only during a time period that the photoions reaches the ion detector. A mass of the neutrals having a desired mass is analyzed from the counted value in the digital manner. A time period required for extracting the photoions is extended to perform the pulse counting without being influenced by the secondary ions which causes noises, so that the mass analysis can be performed with a high sensitivity.