Electron And Positron Scattering From 1,1- C2 H2 F2

1,1-difluoroethylene (1,1- C2 H2 F2) molecules have been studied for the first time experimentally and theoretically by electron and positron impact. 0.4-1000 eV electron and 0.2-1000 eV positron impact total cross sections (TCSs) were measured using a retarding potential time-of-flight apparatus. In order to probe the resonances observed in the electron TCSs, a crossed-beam method was used to investigate vibrational excitation cross sections over the energy range of 1.3-49 eV and scattering angles 90° and 120° for the two loss energies 0.115 and 0.381 eV corresponding to the dominant C-H (2 and 9) stretching and the combined C-F (3) stretching and C H2 (11) rocking vibrations, respectively. Electron impact elastic integral cross sections are also reported for calculations carried out using the Schwinger multichannel method with pseudopotentials for the energy range from 0.5 to 50 eV in the static-exchange approximation and from 0.5 to 20 eV in the static-exchange plus polarization approximation. Resonance peaks observed centered at about 2.3, 6.5, and 16 eV in the TCSs have been shown to be mainly due to the vibrational and elastic channels, and assigned to the B2, B1, and A1 symmetries, respectively. The π* resonance peak at 1.8 eV in C2 H4 is observed shifted to 2.3 eV in 1,1- C2 H2 F2 and to 2.5 eV in C2 F4; a phenomenon attributed to the decreasing CC bond length from C2 H4 to C2 F4. For positron impact a conspicuous peak is observed below the positronium formation threshold at about 1 eV, and other less pronounced ones centered at about 5 and 20 eV. © 2007 American Institute of Physics.12616(1997) Kyoto Protocol to the United Nations Framework Convention on Climate Change, , http://www.cnn.com/SPECIALS/1997/global.warming/stories/treaty, DecemberMitsui, Y., Ohira, Y., Yonemura, T., Takaichi, T., Sekiya, A., Beppu, T., (2004) J. Electrochem. Soc., 151, p. 297Panajotovic, R., Kitajima, M., Tanaka, H., Jelisavic, M., Lower, J., Campbell, L., Brunger, M.J., Buckman, S.J., (2003) J. Phys. B, 36, p. 1615Szmytkowski, C., Kwitnewski, S., Ptasinska-Denga, E., (2003) Phys. Rev. A, 68, p. 032715Brescansin, L.M., MacHado, L.E., Lee, M.-T., (1998) Phys. Rev. A, 57, p. 3504Winstead, C., McKoy, V., (2002) J. Chem. Phys., 116, p. 1380. , 0021-9606 10.1063/1.1429649Winstead, C., McKoy, V., Bettega, M.H.F., (2005) Phys. Rev. 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Electron and positron scattering from 1,1-C₂H₂F₂

1,1-difluoroethylene (1,1-C₂H₂F₂) molecules have been studied for the first time experimentally and theoretically by electron and positron impact. 0.4-1000 eV electron and 0.2-1000 eV positron impact total cross sections (TCSs) were measured using a retarding potential time-of-flight apparatus. In order to probe the resonances observed in the electron TCSs, a crossed-beam method was used to investigate vibrational excitation cross sections over the energy range of 1.3-49 eV and scattering angles 90 degrees and 120 degrees for the two loss energies 0.115 and 0.381 eV corresponding to the dominant C-H (ν₂ and ν₉) stretching and the combined C-F (ν₃) stretching and CH₂ (ν₁₁) rocking vibrations, respectively. Electron impact elastic integral cross sections are also reported for calculations carried out using the Schwinger multichannel method with pseudopotentials for the energy range from 0.5 to 50 eV in the static-exchange approximation and from 0.5 to 20 eV in the static-exchange plus polarization approximation. Resonance peaks observed centered at about 2.3, 6.5, and 16 eV in the TCSs have been shown to be mainly due to the vibrational and elastic channels, and assigned to the B₂, B₁, and A₁ symmetries, respectively. The pi* resonance peak at 1.8 eV in C₂H₄ is observed shifted to 2.3 eV in 1,1-C₂H₂F₂ and to 2.5 eV in C₂F₄; a phenomenon attributed to the decreasing C=C bond length from C₂H₄ to C₂F₄. For positron impact a conspicuous peak is observed below the positronium formation threshold at about 1 eV, and other less pronounced ones centered at about 5 and 20 eV.The work was supported in part by a Grant-in-Aid, the Ministry of Education, Science, Technology, Sport and Culture, Japan, the Japan Society for the Promotion of Science JSPS, and the Japan Atomic Energy Research Institute JAERI. One of the authors C.M. is also grateful to the JSPS for financial support under Grant No. P04064. Another author H.T. acknowledges Dr. T. Ozeki of the JAERI for his encouragement and support during this work. This work was also done under the International Atomic Energy Agency IAEA project for three of the authors C.M., M.H., and H.T.. Two of the authors M.H.F.B. and M.A.P.L. acknowledge support from the Brazilian agency Conselho Nacional de Desenvolvimento Científico e Tecnológico CNPq. MHFB also acknowledges support from the Paraná state agency Fundação Araucária and from FINEP ( under Project No. CT-Infra 1)

Electron and positron scattering from 1,1-C2H2F2

1,1-difluoroethylene (1,1-C2H2F2) molecules have been studied for the first time experimentally and theoretically by electron and positron impact. 0.4-1000 eV electron and 0.2-1000 eV positron impact total cross sections (TCSs) were measured using a retarding potential time-of-flight apparatus. In order to probe the resonances observed in the electron TCSs, a crossed-beam method was used to investigate vibrational excitation cross sections over the energy range of 1.3-49 eV and scattering angles 90 degrees and 120 degrees for the two loss energies 0.115 and 0.381 eV corresponding to the dominant C-H (nu(2) and nu(9)) stretching and the combined C-F (nu(3)) stretching and CH2 (nu(11)) rocking vibrations, respectively. Electron impact elastic integral cross sections are also reported for calculations carried out using the Schwinger multichannel method with pseudopotentials for the energy range from 0.5 to 50 eV in the static-exchange approximation and from 0.5 to 20 eV in the static-exchange plus polarization approximation. Resonance peaks observed centered at about 2.3, 6.5, and 16 eV in the TCSs have been shown to be mainly due to the vibrational and elastic channels, and assigned to the B-2, B-1, and A(1) symmetries, respectively. The pi* resonance peak at 1.8 eV in C2H4 is observed shifted to 2.3 eV in 1,1-C2H2F2 and to 2.5 eV in C2F4; a phenomenon attributed to the decreasing C=C bond length from C2H4 to C2F4. For positron impact a conspicuous peak is observed below the positronium formation threshold at about 1 eV, and other less pronounced ones centered at about 5 and 20 eV. (c) 2007 American Institute of Physics.1261

An Easy-To-Use Simulation Program Demonstrates Variations in Bacterial Cell Cycle Parameters Depending on Medium and Temperature

Many studies are performed on chromosome replication and segregation in Escherichia coli and other bacteria capable of complex replication with C phases spanning several generations. For such investigations an understanding of the replication patterns, including copy numbers of origins and replication forks, is crucial for correct interpretation of the results