Ion formation mechanism in laser desorption ionization of individual nanoparticles

Journal of the American Society for Mass Spectrometry
Melissa S Reinard, Murray V Johnston

Abstract

Covariance mapping is used to study ion formation mechanisms in laser desorption ionization of individual 50 or 220 nm diameter particles having compositions similar to ambient aerosol. Single particle mass spectra are found to vary substantially from particle to particle. This variation is systematic--the energetically preferred ions (e.g., lowest ionization energy, highest electron affinity) are positively correlated with each other and negatively correlated with less preferred ions. For the compositions studied, the average positive ion yield is two to five times greater than the negative ion yield, indicating that free electrons are the main negatively charged species. For many particles, typically 20% to 40% of those analyzed, only positive ions are detected. Smaller particles give fewer negative ions, presumably because the plume is less dense and electron capture is less likely. The results suggest that ion formation occurs by a two stage process. In the first stage, photoionization of laser desorbed neutrals gives cations and free electrons. In the second stage, collisions in the plume cause electron capture and competitive charge transfer. When the particle ablates in a manner giving a dense plume with many collisions,...Continue Reading

References

Nov 18, 2000·Analytical Chemistry·T A SchoolcraftB J Garrison
May 30, 2002·Analytical Chemistry·David B KaneMurray V Johnston
Apr 30, 2003·Rapid Communications in Mass Spectrometry : RCM·Andrew B FeldmanPlamen A Demirev
Sep 12, 2003·Environmental Science & Technology·Derek A LakeAnthony S Wexler
Nov 18, 2003·Analytical Chemistry·Vladimir E FrankevichRenato Zenobi
Jul 1, 2005·Analytical Chemistry·William A HarrisWilliam B Whitten
Mar 1, 2006·Analytical Chemistry·Michael E Sigman, Mary R Williams
Oct 18, 2006·Mass Spectrometry Reviews·Daniel M Murphy
Jun 26, 2007·Journal of Mass Spectrometry : JMS·Klaus-Peter Hinz, Bernhard Spengler

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Citations

Feb 15, 2013·Analytical and Bioanalytical Chemistry·Joseph P Klems, Murray V Johnston
Mar 3, 2009·Proteomics·Jamie ShermanMark P Molloy
Nov 28, 2020·Environmental Pollution·Jovanna ArndtJohn C Wenger
Aug 15, 2018·Journal of the American Society for Mass Spectrometry·Lei LiPing Cheng
Jul 17, 2020·Journal of the American Society for Mass Spectrometry·Alexander PotthoffJens Soltwisch

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