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Laser-SNMS investigations on pyrene using Ga+, Bi1+, Bi3+ and Bi5+ as primary ions and different laser wavelengths and laser power densities for photoionization

Authors


S. Galla, University of Muenster, Institute of Physics, Wilhelm-Klemm-Str. 10, 48149 Muenster, Germany.

E-mail: sebastian.galla@uni-muenster.de

Abstract

Laser secondary neutral mass spectrometry (Laser-SNMS) has been used to simultaneously ionize sputtered secondary neutrals in a nonselective way. To investigate the sputtering and photoionization processes, we examined the dependence of the Laser-SNMS molecular yield on (i) different primary ion bombardment conditions using mono- and polyatomic ions and (ii) the laser parameters wavelength and laser power density. The Laser-SNMS experiments were carried out using Ga+, Bi1+, Bi3+ and Bi5+ as primary ions and two different excimer laser systems for photoionization working at wavelengths of 157 and 193 nm, respectively, with power densities varying between 4 × 106 and 4 × 108 W/cm2. It was found that Bi3+ as primary ion is most suited to investigate organic surfaces. The highest yields could be obtained using a laser wavelength of 157 nm after ionization. Copyright © 2012 John Wiley & Sons, Ltd.

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