Dependence of the ejection velocities of laser-ablated ions on the laser wavelength and fluence

Chau Wen Chou, Randall W. Nelson, Peter Williams

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

Drift measurements of initial ejection velocities of matrix-assisted laser desorption/ionization matrix compounds have been made as a function of ablating laser wavelength and laser fluence. For pulsed laser irradiation just above the matrix ion appearance threshold, initial ejection velocities of protonated molecular ions of an anthranilic acid target increase from ∼1350m/s to ∼1640m/s (kinetic energies of 1.3eV and 1.9eV, respectively] when the ablation laser wavelength is changed from 355nm to 266nm. Increasing the laser fluence per pulse by up to a factor of 10 above threshold results in the appearance of a slower component of the ejected ion flux. The results are interpreted by a photomechanical ejection model in which a photoexcited surface molecule instantaneously becomes larger and recoils away from the surface.

Original languageEnglish (US)
Pages (from-to)305-314
Number of pages10
JournalEuropean Journal of Mass Spectrometry
Volume15
Issue number2
DOIs
StatePublished - Apr 30 2009

Keywords

  • Initial velocities
  • Ion ejection mechanism
  • Laser fluence dependence
  • Laser wavelength dependence
  • MALDI

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Spectroscopy

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