Application of laser induced photoemission electron in time-of-flight mass spectrometry

Abstract

Multicharged ions of Ar and NO were observed in multiphoton ionization (MPI) experiments while a focused laser beam struck extractor grid of time-of-flight mass spectrometry (TOF-MS). A special photoemission electron impact ionizer was designed. This ionizer made it possible to investigate the mechanism of photoelectron impact ionization. The experiment showed that the multicharged ions could be produced only by the photoelectron impact, probably ionized step by step. With this special ionizer high Rydberg states ( n ∼ 40 − 100) of atoms and/or molecules were, for the first time, observed in the TOF-MS. The yield ratio of Rydberg states to ions was strongly dependent of the laser power and the energy of the photoemission electrons. Our experiment results showed that this ionizer could be an effective method for producing multicharged ions and high Rydberg states of atoms and molecules.