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  • 82.50  (9)
  • 73.60.Fw  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Carbon-13 separation by IRMPD of trifluoromethane-d0 and -d1 (1985)
    Springer
    Applied physics 36 (1985), S. 111-113 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 82.50
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00694697
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  • 2
    Digitale Medien
    Digitale Medien
    Isotopically selective CVD of silicon by IRMPD of Si2F6 (1988)
    Springer
    Applied physics 47 (1988), S. 243-245 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 82.50 ; 82.65
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The IRMPD of Si2F6 by a CO2 TEA laser was applied to isotopically selective CVD of silicon. A white film, probably consisting of polymers of SiF2, was deposited on a metal foil during the irradiation of natural Si2F6 with the laser radiation at 951.19 cm−1 and about 1.5 J cm−2. Upon heating, the film became dark brown, evolving SiF4. The30Si content was found to be as high as about 20%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00697344
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  • 3
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): 82.50 ; 33
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00694544
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  • 4
    Digitale Medien
    Digitale Medien
    Enrichment of 13C by IRMPD of CBr2F2 (1991)
    Springer
    Applied physics 52 (1991), S. 266-272 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 82.50
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: 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%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00325403
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  • 5
    Digitale Medien
    Digitale Medien
    Infrared emissions in the CO2-laser-induced photolysis of trifluoromethane-d and mixtures of trifluoromethane-d and -h (1983)
    Springer
    Applied physics 32 (1983), S. 85-92 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 82.50
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Time-resolved infrared emission spectra in the wavelength region of 2–5 μm were measured for the CO2-laser-induced photolysis of trifluoromethane-d (CDF3) and its mixtures with trifluoromethane-h (CHF3). The reactant pressures were 0.1–20 Torr at room temperature; some collisions were expected to occur within the laser-pulse duration. The emissions due to vibrationally excited CDF 3 * (C-D stretching mode and probably combination mode) and DF* were observed at the same time for the irradiation of pure CDF3. DF* should be produced in the unimolecular decomposition of CDF 3 * . The dependences of the DF* emission on the experimental condition are explicable on the assumption that the collisional energy transfer followed by the decomposition of CDF3 plays an important role in the present IRMPD, besides its direct multiple-photon decomposition. The mixture of CDF3 and CHF3 showed the emissions due to HF* and CHF 3 * in addition to DF* and CDF 3 * . The ratio between the DF* and HF* emission intensities,I DF/I HF, was examined as a function of pressure. The pressure dependences were similar to those of the selectivity determined previously from the concentration changes of CDF3 and CHF3. The irradiation of mixtures with a long furation pulse (80 ns fwhm with a 2μs) resulted in a marked decrease inI DF/I HF.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00688549
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  • 6
    Digitale Medien
    Digitale Medien
    13C-selective two-stage IRMPD of mixtures of CHClF2 and HI (1990)
    Springer
    Applied physics 50 (1990), S. 385-392 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 82.50
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00325091
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  • 7
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): 82.50
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00324949
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  • 8
    Digitale Medien
    Digitale Medien
    Practical separation of silicon isotopes by IRMPD of Si2F6 (1991)
    Springer
    Applied physics 53 (1991), S. 199-202 
    Details
    ISSN: 1432-0649
    Schlagwort(e): 82.50
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Large-scale silicon isotope separation based on the IRMPD of natural Si2F6 has been carried out using a commercially available high power CO2 TEA laser and a flow reaction system. The decomposition product SiF4 containing 19–33% of 30Si was obtained at a production rate of 1.5×10−2−2.6×10−2 mol·h−1, depending on experimental parameters such as laser wavelength, laser fluence, pressure, and flow rate. SiF4 containing 12% of 29Si was obtained under slightly different conditions, i.e., at a shorter wavelength than that for 30Si. When 39% of Si2F6 was decomposed at a slow flow rate, residual Si2F6 was found to have 99.7% of 28Si. The production rate was 4.2×10−2 mol·h−1.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00357136
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  • 9
    Digitale Medien
    Digitale Medien
    Mechanism of isotope scrambling for CO2 laser photolysis of trifluoremethane-h and-d mixtures (1981)
    Springer
    Applied physics 25 (1981), S. 1-6 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 82.50
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The mechanism of isotope scrambling was studied for infrared multiphoton dissociation of trifluoromethane-h (CHF3) and-d (CDF3) mixtures by a CO2 TEA laser. The CO2 laser was tuned to the R(14) line of the 001–100 transition, where CDF3 absorbs the light selectively. Although the highly selective decomposition of CDF3 occurred at low partial pressures of CDF3, significant decomposition of CHF3 was also observed with increasing pressure of CDF3. The selectivity (s) was found to depend only on the pressure of CDF3, a resonant molecule, but not on that of CHF3, an off-resonant molecule. The mechanism involving the formation of two kinds of vibrationally excited molecules, unimolecular decomposition (rate constantk 2 ),V-V energy transfer (k 3b), and collisional deactivation leads to the simple relationship,s=1+(k 2 /k 3b)/[CDF3], which can explain qualitatively the observed results. The ratiok 2 /k 3b has values of 20–200 Torr, probably depending on experimental conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00935383
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  • 10
    Digitale Medien
    Digitale Medien
    A thin-film transistor with a very thin a-Si:H layer and its application for an LC panel (1986)
    Springer
    Applied physics 41 (1986), S. 311-314 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 73.40.Qv ; 73.60.Fw ; 86.60.Pg
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract One of the disadvantages of applying an a-Si:H thin-film transistor (TFT) to an active matrix-addressed liquid crystal (LC) panel is that a TFT with an a-Si:H has a very large photo-leakage current because of the high photo-conductivity of an a-Si:H itself. We have tried decreasing the photo-leakage current by varying the thickness of an a-Si:H layer (L) in TFTs and investigated the characteristics of TFTs, mainly drain voltage versus drain current containing photo-leakage current (I ph). As a result, it is shown that lnI ph is proportional to InL, and its gradient is 1.5–2.0. We assume that the thinner an a-Si:H layer is, the more effective the recombination of carriers at the interface states is forI ph. We have applied TFT with a very thin a-Si:H layer (∼30nm) to a full-color active matrix-addressed LC panel for a moving picture display and realized a display of good quality under illuminated condition of 5×104lx without a shading layer in it.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00616054
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