Molecular beam photofragment translational

While one might expect that the techniques developed for photodissociation studies of closed-shell molecules would be readily adaptable to free radicals, this is not the case. A successful photodissociation experiment often requires a very clean source for the radical of interest in order to minimize background problems associated with photodissociating other species in the experiment. Thus, molecular beam photofragment translation spectroscopy, which has been applied to innumerable closed-shell species, has been used successfully on only a handful of free radicals. With this problem in mind, we have developed a conceptually different experiment [4] in which a fast beam of radicals is generated by laser photodetachment of mass-selected negative ions. The radicals are photodissociated with a second laser, and the fragments are detected in coinci-... 

The photolysis of CH3NO2 by 193 nm laser light was studied by product emission spectroscopy and molecular beam photofragment translational energy spectroscopy by Butler et al. (119). Blais (120) also studied the photolysis by the TOF method. The primary process is... 

Molecular beam photofragment translational energy spectroscopy has been used by Hepburn et to elucidate the photodissociation mechanisms of Si glyoxal. They presented evidence for predissociation of S, glyoxal in the absence of collisions and for the existence of three distinct dissociation pathM(ays. The major dissociation mechanisms were shown to lead to the formation of H2CO + CO and 2CO-I-H2, with a third minor channel producing CO 3-an isomer of H2CO, possibly hydroxymethylene. 

J. Helpburn, Photofragment translational spectroscopy, Atomic and Molecular Beam Methods, ed. G. Scoles (Cambridge Press). 

Velocity Distribution of the Parent Molecular Beam. To obtain the translational velocity distribution from TOF spectra of photofragments, it is necessary to measure the velocity distribution of the parent molecular beam. In these measurements, the parent molecular beam is set at 0,3 = 0° and the detector is reduced to 0.127 mm. Two methods are used here. The first uses a TOF chopper wheel to chop the parent beam to generate a narrow parent gas beam pulse. The TOF spectrum resulting from this gas... 

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