Time-resolved photodissociation

Lin C Y and Dunbar R C 1994 Time-resolved photodissociation rates and kinetic modeling for unimolecular dissociations of iodotoluene ions J. Rhys. Chem. 98 1369-75... 

The studies of naphthalene and bromonaphthalene ions are companion studies in that they both access the thermochemistry of the naphthyl cation, C, oH, using a combination of TRPD energy-specific rate measurements with deconvoluted time-resolved photodissociation (TPIMS) results [Equations (12) and (13)]. In this... 

Dunbar, R.C. (1987) Time-resolved Photodissociation of Chlorobenzene Ion in the ICR Spectrometer. J. Phys. Chem. 91 2801-2804. 

Faulk, J.D., Dunbar, R.C. (1992) Time-resolved Photodissociation of Gas-phase Ferrocene Cation Energetics of Fragmentation and Radiative Relaxation Rate at Near-thermal Energies. J. Am. Chem. Soc. 114 8596-8600. 

Dunbar, R.C., Lifshitz, C. (1991) Slow Time-resolved Photodissociation of p-Iodotoluene Ion. J. Chem. Phys. 94 3542-3547. 

Kim, B., Shin, S.K. (2002) Time-resolved Photodissociations of lodotoluene Radical Cations. J. Phys. Chem. A 106 9918-9924. 

Cui, W., Hu, Y., Lifshitz, C. (2002) Time Resolved Photodissociation of Small Peptide Ions. Combining Laser Desorption with Ion Trap/Reflectron TOP Mass Spectrometry. Eur. Phys. J. D 20 565-571. 

Short-lived reaction intermediates and products resulting fi-om light flash photolysis have been detected using TOF-MS [76]. A flash lamp was used to induce photochemical reactions of the reactant gases in a reaction vessel. The generated species, such as radicals, could be immediately (in approximately milliseconds) detected by TOF-MS [76]. In other work, a laser beam was combined with an ion cyclotron resonance mass analyzer to follow the process of photodissociation [77]. The dissociation rates and branching ratios for naphthalene ion were measured by means of the time-resolved photodissociation approach. The above-mentioned approaches [76,77] are limited to detection of species generated from gas-phase substrates. 

Slow dissociation rates (10 -10 s ) have been measured in Dunbar s laboratory by time-resolved photodissociation, which consists of trapping ions in an ICR cell during a variable delay time after a phot-odissociating photon pulse. The technique called time-resolved photoionization mass spectrometry , developed by Lifshitz, consists of trapping photoions in a cylindrical trap at very low pressure to avoid bimolecular collisions, and then ejecting them into a mass filter after a variable delay covering the microsecond to millisecond range. When the dissociation rate constant becomes lower than ca. 10 s competition with infrared fluorescence takes place and limits the lifetime of the decomposition process. This has to be taken into account to extract the dissociation rate constant from the experimental data. 

Figure 2 Reaction mechanism for the loss of iodine from the p-iodotoluene cation, after the work of Lin and Dunbar Lin CY and Dunbar RC (1994) Time-resolved photodissociation rates and kinetic modelling for unimolecular dissociations of iodotoluene Ions. The Journal of Physical Chemistry 98 1369-1375.

Yoon, S. H. Chung, Y. J. Kim, M. S. Time-resolved photodissociation of singly protonated peptides with an arginine at the N-terminus a statistical interpretation. J. Am. Soc. Mass Spectrom. 2008, 19, 645-655. 

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