ArF excimer laser multiphoton-ionization mass spectrometry of organic molecules

Threshold photoelectron–photoion coincidence spectroscopy study of CHCl2F+, CHClF+2 and CH2ClF+: Steric influence of the chlorine, fluorine and hydrogen atoms

“…We note that a two-photon absorption study on this molecule, using an ArF excimer laser providing 193 nm photons, yielded CHF 2 + as the sole ion produced. 31 Two photons of this wavelength correspond to ionization at 12.85 eV, which corroborates our observations. From close examination of the TOF-MS of this fragment, it is apparent that the signal is solely due to CHF 2 + at low photon energies.…”

Continued Investigations of New Concepts for Improved Spectrochemical Analysis

“…A second approach is to use nonresonant photoionization to ionize all compounds whose ionization potentials lie below a threshold value determined by the photon energy. This can be accomplished using a nonresonant multiphoton [80,81] Evaluation of the H 2 laser photoionization technique as a selective source for analytical mass spectrometry has recently been made in our laboratory [22,89]. The experimental system used in this study is shown in Figure 21 and consists of the laser, coupled with a simple linear time-offlight mass spectrometer.…”

“…On the other hand, nonresonant multiphoton ionization generally results in fragmentation of the parent ion, producing spectra that resemble those from low-energy electron impact (81].…”

Lasers and Mass Spectrometry

“…Unlike the photoionization technique, how ever, the differential vacuum pumping associated with vacuum UV is avoid ed, and very high fluxes can be used. DeCorpo et al (26) have obtained ArF excimer laser mass spectra for a num ber of organic molecules. Ionization takes place by the usual photoioniza tion channels of direct ionization or autoionization from a superexcited state, except that two photons are in volved.…”

“…The experiments discussed above have involved TOF instruments (19,(21)(22)(23) or quadrupole analyzers (18,26). Lichtin et al (23) have noted that for TOF analyzers the "time lag focus ing" technique first described by Wiley and McLaren (27) improves resolution for ions produced with an energy spread somewhat larger than EI methods.…”