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Gas phase activation energy for unimolecular dissociation of biomolecular ions determined by Focused RAdiation for Gaseous Multiphoton ENergy Transfer (FRAGMENT)
Author(s) -
Freitas Michael A.,
Hendrickson Christopher L.,
Marshall Alan G.
Publication year - 1999
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/(sici)1097-0231(19990815)13:15<1639::aid-rcm691>3.0.co;2-s
Subject(s) - chemistry , dissociation (chemistry) , gas phase , ion , radiation , energy transfer , fragment (logic) , photochemistry , chemical physics , organic chemistry , nuclear physics , programming language , physics , computer science
We present a novel approach for the determination of activation energy for the unimolecular dissociation of a large (>50 atoms) ion, based on measurement of the unimolecular dissociation rate constant as a function of continuous‐wave CO 2 laser intensity. Following a short (∼ 1 s) induction period, CO 2 laser irradiation produces an essentially blackbody internal energy distribution, whose ‘temperature’ varies inversely with laser intensity. The only currently available method for measuring such activation energies is blackbody infrared radiative dissociation (BIRD). Compared with BIRD, FRAGMENT: (a) eliminates the need to heat the surrounding ion trap and vacuum chamber to each of several temperatures (each requiring hours for temperature equilibration); (b) offers a three‐fold wider range of effective blackbody temperature; and (c) extends the range of applications to include initially cold ions (e.g., gas‐phase H/D exchange). Our FRAGMENT‐determined activation energy for dissociation of protonated bradykinin, 1.2 ± 0.1 eV, agrees within experimental error to the value, 1.3 ± 0.1 eV, previously reported by Williams et al. from BIRD experiments. Copyright © 1999 John Wiley & Sons, Ltd.