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Caltech Authors (158.172 recursos)

Repository of works by Caltech published authors.

Type = Article

Mostrando recursos 21 - 23 de 23

  1. Efficient multiphoton dissociation of CF3I+ in the metastable X-tilde 2E1/2 excited state using cw infrared laser radiation

    Thorne, L. R.; Beauchamp, J. L.
    Evidence for the multiphoton dissociation of an electronic metastable state of CF3I+ with CO2 laser radiation is presented. Only those ions possessing sufficient internal excitation before irradiation can be dissociated. Photodissociation results primarily from resonant absorption by the nu1 vibrational mode of CF3I+ in the higher of the two, spin–orbit levels of the ground electronic state Xbar^2 E1/2. Only the lowest energy decomposition channel is observed; this yields CF + 3 and I. Spin–orbit and vibrational relaxation compete with photodissociation. At CF3I pressures below 2×10^−7 Torr, the collisional relaxation rate is proportional to CF3I pressure kc = (3.1±0.4)×10^−9 cm^3 molecule^−3...

  2. Vibrational overtone initiated unimolecular dissociation of HOCH_2OOH and HOCD_2OOH: Evidence for mode selective behavior

    Matthews, Jamie; Fry, Julie L.; Roehl, Coleen M.; Wennberg, Paul O.; Sinha, Amitabha
    The vibrational overtone induced unimolecular dissociation of HMHP (HOCH2OOH) and HMHP-d2 (HOCD2OOH) into OH and HOCH2O (HOCD2O) fragments is investigated in the region of the 4nuOH and 5nuOH bands. The unimolecular dissociation rates in the threshold region, corresponding to the 4nuOH band, exhibit measurable differences associated with excitation of the OH stretch of the alcohol versus the peroxide functional group, with the higher energy alcohol OH stretching state exhibiting a slower dissociation rate compared to the lower energy peroxide OH stretch in both HMHP and HMHP-d2. Predictions using the Rice–Ramsperger–Kassel–Marcus theory give rates that are in reasonably good agreement with...

  3. Acidity enhances the formation of a persistent ozonide at aqueous ascorbate/ozone gas interfaces

    Enami, Shinichi; Hoffmann, M. R.; Colussi, A. J.
    The pulmonary epithelium, like most aerial biosurfaces, is naturally protected against atmospheric ozone (O3) by fluid films that contain ascorbic acid (AH2) and related scavengers. This mechanism of protection will fail, however, if specific copollutants redirect AH2 and O3(g) to produce species that can transduce oxidative damage to underlying tissues. Here, the possibility that the synergistic adverse health effects of atmospheric O3(g) and acidic particulate matter revealed by epidemiological studies could be mediated by hitherto unidentified species is investigated by electrospray mass spectrometry of aqueous AH2 droplets exposed to O3(g). The products of AH2 ozonolysis at the relevant air–water interface...

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