Lawrence Berkeley National Laboratory Recent Work Title INFRARED LASER MULTIPLE-PHOTON DISSOCIATION OF CDCl (original) (raw)
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The Journal of Physical Chemistry, 1989
A TEA CO, pulsed laser was used to study the infrared multiple-photon dissociation (IRMPD) of CDCl, in equimolar isotopic mixtures of CDC13/CHC13 and with the addition of Ar and Xe. The dependence of the reaction probability per pulse on CDC13 pressure in the gas mixture was studied for different laser fluences. Lower limit values of isotopic selectivity were determined. The experimental results were modeled by using an energy-grained master equation with explicit consideration of rotational and anharmonic bottlenecks. Model calculations predict that the average energy transferred in a deactivating collision, (AE),+ increases with increasing CDCI3 vibrational excitation.
Chemical Physics Letters, 1982
Infrared multiple-photon dissociation of CTC13 was investigated using a pulsed CO2 laser-pumped NH3 laser at 12.08 /am. No evidence of any CDC13 depletion or decomposition product was observed in photolyzed CTCI3/CDC13 mixtures. A lower limit of the single-step T/D enrichment factor,/3, was found to be ~ 165, based on the sensitivity in measuring CDCI 3 depletion. The low-fluence CTC13/CDC13 optical selectivity in absorption is >9000 at the 835 cm -1 CTCI 3 v 4 peak.
Chloroform Infrared Multiphoton Dissociation in the Presence of O2 and NO2¶
Photochemistry and Photobiology, 2005
The infrared multiphoton dissociation (IRMPD) of CDC13 in the presence of O2 and NOz as acceptor gases has been studied. We have worked with both pure CDC13 and mixtures with CHCls. The reaction mechanism following IRMPD of CDC13 is discussed in detail. CCl2O, CC4 and DCl were found to be the main products. With added Oz, the observed CDC13 dissociation was larger than with nonoxygenated acceptor gases. The reaction mechanism probably involves a catalytic cycle initiated by the oxidation of CC13. With the aim of discriminating the different CDCI, dissociation mechanisms, the IRMPD of CDCb in the presence of NO2 was first studied. In order to make evident the CDC13 dissociation produced by the catalytic cycle, we then studied the IRMPD of CDCl3 in mixtures with CHCI3 with Oz as the acceptor gas. In this case, the dissociation mechanism subsequent to IRMPD is evidenced in the competence between the two isotopic species.
2015
A moderate-resolution infrared multiple photon dissociation (IRMPD) spectrum of protonated bis(2-methoxyethyl) ether (diglyme) was obtained using a grating-tuned CO2 laser. The experimental spectrum compares well with one calculated theoretically at the MP2 level and exhibits defined peaks over the span of the CO2 laser output lines as opposed to a relatively featureless spectrum over this wavelength range obtained using free electron laser infrared radiation. The lowest energy structure corresponding to the calculated vibrational spectrum is consistent with structures previously calculated at the same level of theory. Alternative structures were calculated at lower levels of theory for comparison and investigation of the energetics of proton-heteroatom interactions. Broadening of the IRMPD action spectrum due to energetic phenomena characteristic of proton bridges was not observed and thus did not obscure the correlation between theoretical calculations and experimentally determine...
Infrared Multiple Photon Dissociation of Chloromethyltrifluorosilane
Photochemistry and Photobiology, 2009
Infrared multiphoton absorption and dissociation of chloromethyltrifluorosilane molecules under the action of pulsed transversely excited atmospheric pressure CO 2 laser were experimentally studied. Dissociation products were analyzed. The dissociation proceeds via chlorine atom transfer from carbon to silicone. High degrees of silicon isotope separation were achieved. The presence of a-chlorine atom in a silicon organic compound brings about a significant improvement in multiple photon dissociation characteristics and an essential increase in isotopic selectivity.
Journal of Photochemistry and Photobiology A: Chemistry, 2003
In contrast to the electronically excited propynal at 193 nm undergoing aldehyde C-H and C-C bond ruptures, on pulsed TEA-CO 2 laser irradiation, multiphoton vibrationally excited propynal undergoes concerted dissociation generating CO and acetylene. Vibrational excitation in the CO product is detected immediately following the CO 2 laser pulse by observing infrared (IR) emission at 4.7 m. The decay of the IR emission was studied as a function of propynal pressure. A vibrational-vibrational relaxation rate constant of CO (ν ≥ 1) by propynal is found to be 1540 ± 200 Torr −1 s −1 . With the collisionless dissociation of propynal, the evaluated unimolecular rate constant of (1.5 ± 0.2) × 10 7 s −1 , vis-a-vis RRKM calculations, gives an average IR multiphoton excitation level of propynal as 75 ± 4 kcal mol −1 .