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Keywords:

  • matrix-assisted laser desorption/ionization by infrared laser;
  • density functional theory;
  • electron-correlated second-order Møller–Plesset calculation;
  • IR absorption spectra of solid structure and isolated molecule;
  • vibrational modes

Abstract

To investigate the correlation between the wavelength dependence of ionization threshold fluence of target molecule in matrix-assisted laser desorption/ionization by infrared (IR) laser and the IR absorption spectrum of matrix molecule, we have analyzed the IR absorption spectra of four matrix molecules using density functional theory and correlated ab initio molecular orbital method. The calculated IR absorption spectra of the isolated molecules showed more qualitative correlation with the wavelength dependence of ionization threshold fluence than those of the solid state structures. We can consider that a portion of matrix molecules lost the ordered crystal structure and that the transition to the diluted or isolated state occurred at the early process of IR laser irradiation. © 2012 Wiley Periodicals, Inc.