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Multiphoton ionization and photodissociation at the second‐order space focus in a time‐of‐flight mass spectrometer: The amino acid tryptophan
Author(s) -
Dey Michael,
Grotemeyer Jürgen
Publication year - 1994
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210291114
Subject(s) - photodissociation , ionization , fragmentation (computing) , ion , chemistry , mass spectrometry , mass spectrum , tryptophan , atomic physics , time of flight , laser , analytical chemistry (journal) , photochemistry , optics , physics , amino acid , chromatography , biochemistry , organic chemistry , computer science , operating system
Neutral IR‐desorbed molecules of the amino acid tryptophan entrained in a supersonic beam were post‐ionized by multiphoton ionization (MUPI) in the gas phase. Variations in the intensity of the ionization laser produced different degrees of fragmentation observed in the time‐of‐flight mass spectra of tryptophan according to the ladder‐switching model for MUPI fragmentation. From the number of absorbed photons the upper values for the appearance energies of specific fragment ions were obtained. A complete fragmentation pathway of tryptophan was established by using photodissociation of molecular ions and fragment ions formed by MUPI. Photodissociation was successfully performed by secondary excitation with a UV laser at the second‐order space focus of a reflection time‐of‐flight instrument. A fragmentation tree for a laser‐desorbed molecule obtained in a laser tandem time‐of‐flight instrument is shown for the first time.