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  • 33.80.Wz  (1)
  • PACS: 82.40Z; 82.50  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Isotope-selective IR multiphoton dissociation of CHClF2 in the presence of NO2 (1997)
    Springer
    Applied physics 65 (1997), S. 577-582 
    Details
    ISSN: 1432-0649
    Keywords: PACS: 82.40Z; 82.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 2 to the CHClF2/He mixture irradiated by a Q-switched CO2 laser leads to oxidation of the dissociation product according to the reaction: CF2+NO2→COF2+NO. The resulting COF2 with a 13C content near 50% is easy to convert to CO2 or CO for further enrichment by a nonlaser process. We measured the dependence of the fraction of dimerised CF2 on NO2 pressure pNO2 and the amount of NO2 required to suppress dimerisation on the dissociation yield. Both agree with a kinetic model using known rate constants. For the range of the dissociation parameters (13CF2 yield of 10% per pulse, isotope selectivity of 130) of practical interest, 95% of the CF2 produced is oxidized at pNO2≈1/2pCHClF2. In the absence of NO2, major (20%–35%) losses of CF2 at the metal walls of the irradiation system were observed. Addition of NO2 suppresses them. For comparison, we also used O2 as a scavenger in CHClF2 dissociation. NO2 is by orders of magnitude more efficient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003400050316
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  • 2
    Electronic Resource
    Electronic Resource
    Isotopically selective IR multiphoton dissociation of 1,3,5-trioxane (1996)
    Springer
    Applied physics 62 (1996), S. 203-212 
    Details
    ISSN: 1432-0649
    Keywords: 33.80.Wz
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Searching for oxygen-isotope selectivity, we investigated the infrared multiphoton dissociation of the formaldehyde trimer around 10 µm, in a range where the molecule has a degenerate and a non-degenerate CO stretch vibration and a degenerate CH2 deformation vibration. In the region of the two latter, the wavelength dependence of the dissociation yield exhibits sharp structures. They were assigned ton-photon resonances (n = 2, 3, 5) by the help of the IR spectrum in the fundamental and overtone region. The O and C selectivities were very small (1.05) near the non-degenerate CO stretch band, but surprisingly large (2–4) in the CH2 deformation, which has no isotopic shift. The selectivity is not controlled by the first (n-photon) excitation step, but only by a later step. Its assignment is attempted. The pressure dependence of the dissociation is peculiar: Only after an initial decrease, the yield exhibits the usual rise with pressure. We attribute the decrease to a relaxation which perturbs the two-photon resonance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01081126
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