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  • 1
    Electronic Resource
    Electronic Resource
    Carbon-13 separation by IRMPD of trifluoromethane-d0 and -d1 (1985)
    Springer
    Applied physics 36 (1985), S. 111-113 
    Details
    ISSN: 1432-0649
    Keywords: 82.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Carbon-13 isotope selectivities and specific decomposition yields in the infrared multiple-photon decomposition of CHF3 and CDF3 were examined as a function of wave number using a CO2 TEA laser. The observed maximum selectivities were 30 for CHF3 and 55 for CDF3. The specific decomposition yields in CDF3 were considerably larger than those in CHF3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00694697
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Production of highly concentrated 13C by continuous two-stage IRMPD. CBr2F2/HI, CCl2F2/HI, and CBrClF2/HI mixtures (1989)
    Springer
    Applied physics 49 (1989), S. 503-512 
    Details
    ISSN: 1432-0649
    Keywords: 82.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Difluoromethane CH2F2 containing 90–98% 13C was obtained in the selective IRMPD of mixtures of CBr2F2/HI, CCl2F2/HI, and CBrClF2/HI. In CBr2F2/HI mixtures, the intermediate product CHBrF2 resulting from the reaction between the initial decomposition fragment CBrF2 and HI underwent secondary selective IRMPD to form highly 13C-enriched CH2F2 in continuous laser irradiation. The intermediate product in the mixtures of CCl2F2/HI and CBrClF2/HI was found to be CHClF2, but no significant secondary photodecomposition in CBrClF2/HI mixtures occurred owing to the low absorption cross section of CHClF2 at the adopted laser frequencies and fluences. The observed decomposition probabilities and selectivities under different conditions with respect to laser frequency, fluence, and partial pressures of halogenated difluoromethanes and HI suggest that CBr2F2 is one of the better candidates for practical 13C separation by IRMPD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00324949
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    13C-selective two-stage IRMPD of mixtures of CHClF2 and HI (1990)
    Springer
    Applied physics 50 (1990), S. 385-392 
    Details
    ISSN: 1432-0649
    Keywords: 82.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The 13C-selective infrared multiple-photon decomposition (IRMPD) of mixtures of CHClF2 and HI was examined in collimated and focused beam geometries using a CO2TEA laser. The carbon-containing products were CH2F2 and CHF2I. The former product showed remarkably high 13C atom concentrations beyond 95% under selected experimental conditions, while the latter contained 25% or less. The observed results can be explained satisfactorily in terms of the consecutive two-stage IRMPD process occurring in a single irradiation procedure, where the first-stage IRMPD of natural CHClF2 produces 13C-enriched CHF2I via the insertion of the initial decomposition fragment CF2 into HI, and the second stage is the subsequent 13C-selective IRMPD of the CHF2I to form a CHF2 radical and an I atom. The CHF2 radical reacts with HI to form CH2F2. Decomposition probabilities of 12CHClF2 and 13CHClF2 were measured as a function of laser fluence to optimize enrichment conditions. Furthermore, partial decomposition probabilities or relative production yields were measured as functions of laser line, pressure of HI, and pressure of CHClF2. Both stages showed high 13C selectivities in the irradiation with the laser radiation around 1040 cm−1 and at fluences below 4 J cm−2. This mixture is one of the most promising chemical systems for the production of highly enriched 13C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00325091
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  • 4
    Electronic Resource
    Electronic Resource
    First-stage enrichment in CO2-laser-induced13C separation by a two-stage IRMPD process: IRMPD of CHClF2/Br2 mixtures (1989)
    Springer
    Applied physics 48 (1989), S. 427-435 
    Details
    ISSN: 1432-0649
    Keywords: 82.50 ; 33
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have been studying the practical CO2-laser-induced13C separation by a two-stage IRMPD process. The IRMPD of natural CHClF2 in the presence of Br2 mainly produced CBr2F2, which was found to be highly enriched with13C. The yield and13C-atom fraction of CBr2F2 were examined as functions of pulse number, laser line, laser fluence, total pressure, and Br2 pressure using a CO2 TEA laser with an output less than 1 J pulse−1 in order to optimize experimental conditions for13C separation. For example, we obtained CBr2F2 at a13C concentration of 55% in the irradiation of the mixture of 100-Torr CHClF2 and 10-Torr Br2 with the laser radiation at a wavenumber of 1045.02 cm−1 and at a fluence of 3.4 J cm−2. The mechanism for the IRMPD is discussed on the basis of observed results. Using 8-J pulses, we were able to obtain 1.9×10−4 g of13C-enriched CBr2F2 (13C-atom fraction, 47%) per pulse under selected conditions. It is possible to produce 90% or higher13C by the second-stage IRMPD of the CBr2F2 in the presence of oxygen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00694544
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  • 5
    Electronic Resource
    Electronic Resource
    Enrichment of 13C by IRMPD of CBr2F2 (1991)
    Springer
    Applied physics 52 (1991), S. 266-272 
    Details
    ISSN: 1432-0649
    Keywords: 82.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The CO2-laser-induced infrared multiple photon decomposition of natural CBr2F2 in the presence of oxygen has been examined as a function of pulse number (30–1500), reactant pressures (CBr2F2, 10–150 Torr and O2, 5–90 Torr), laser line [9P(8)–9P(32)], and laser fluence (1–3 J cm−2) to optimize irradiation conditions for 13C-enrichment. CF2O was the main carbon containing product and afterwards was converted into CO2 via hydrolysis. A small amount of C2Br2F4 was detected only under extreme conditions, for example, at high laser fluences or wavenumbers close to an absorption band. The 13C-atom fraction of the final product CO2 was found to be 20–80%, depending on experimental conditions. The two-stage IRMPD process proposed previously has been examined in further detail in the present study. First, CBr2F2 containing about 30% of 13C was prepared in the 13C-selective IRMPD of natural CHClF2 in the presence of Br2. The second-stage IRMPD of the CBr2F2 in the presence of oxygen under selected conditions resulted in the high enrichment of 13C beyond 90%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00325403
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    Paper (German National Licenses)
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