Statistical vs. non-statistical deactivation pathways in the UV photo-fragmentation of protonated tryptophan-leucine dipeptide.
The excited state dynamics of protonated tryptophan-leucine ions WLH+, generated in an electrospray source, is investigated by photo-induced fragmentation in the gas phase, using femtosecond laser pulses. Two main features arise from the experiment. Firstly, the initially excited pipi* state decays very quickly with 2 time constants of 1 and 10 ps. Secondly, the transient signals recorded on different fragments are not the same which indicates two competing primary fragmentation processes. One involves a direct dissociation from the excited state that gives evidence for a non-statistical deactivation path. The other is attributed to a statistical decay following internal conversion to the ground electronic surface.
Laboratoire de Physique des Lasers du CNRS-Université Paris 13, Institut Galilée, 93430 Villetaneuse, France. gregoire@lpl.univ-paris13.fr
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Grégoire
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Kang
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Dedonder-Lardeux
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Jouvet
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Desfrançois
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Onidas
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Lepere
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Fayeton
D004151:Dipeptides / Q000737:chemistry* / Q000528:radiation effects*; D007259:Infrared Rays; D007700:Kinetics; D007930:Leucine / Q000737:chemistry* / Q000528:radiation effects; D013058:Mass Spectrometry; D008962:Models, Theoretical; D010455:Peptides / Q000737:chemistry* / Q000528:radiation effects; D010782:Photolysis; D011522:Protons; D013997:Time Factors; D014364:Tryptophan / Q000737:chemistry* / Q000528:radiation effects; D014466:Ultraviolet Rays
D004151:Dipeptides; D010455:Peptides; D011522:Protons; C509811:tryptophan-leucine; D014364:Tryptophan; D007930:Leucine