Positron annihilation in TiO2 rutile crystal is studied by an assumption that a positron binds with valance electrons of a titanium dioxide to form a pseudo TiO2-positron molecule before it annihilates with these elec...Positron annihilation in TiO2 rutile crystal is studied by an assumption that a positron binds with valance electrons of a titanium dioxide to form a pseudo TiO2-positron molecule before it annihilates with these electrons. The orbital modification consisting of explicit electron-positron and electron-electron correlation in each electronic orbital is used for the electrons and positron wave functions. By these wave functions, the calculation results of the positron lifetimes in unmitigated and defective TiO2 crystals are about 170 ps, 266 ps and 243 ps, respectively. These results are in good agreement with experimental data of the positron lifetimes in vacancies of TiO2 from 180 ps to 300 ps.展开更多
The nuclear mean-field potential built up during the ^(12)C+^(12)C and ^(16)O+^(16)O collisions at low energies relevant for the carbon-and oxygen-burning processes is constructed within the double-folding model(DFM) ...The nuclear mean-field potential built up during the ^(12)C+^(12)C and ^(16)O+^(16)O collisions at low energies relevant for the carbon-and oxygen-burning processes is constructed within the double-folding model(DFM) using the realistic ground-state densities of^(12)C and^(16)O, and CDM3Yn density-dependent nucleon–nucleon(NN) interaction. The rearrangement term, indicated by the Hugenholtz–van Hove theorem for the single-particle energy in nuclear matter, is properly considered in the DFM calculation. To validate the use of the density-dependent NN interaction at low energies, an adiabatic approximation was suggested for the dinuclear overlap density. The reliability of the nucleus–nucleus potential predicted through this low-energy version of the DFM was tested in the optical model(OM) analysis of the elastic^(12)C+^(12)C and ^(16)O+^(16)O scattering data at energies below 10 MeV/nucleon.These OM results provide a consistently good description of the elastic angular distributions and 90 excitation function. The dinuclear mean-field potential predicted by the DFM is further used to determine the astrophysical S factor of the ^(12)C+^(12)C and ^(16)O+^(16)O fusions in the barrier penetration model. Without any adjustment of the potential strength, our results reproduce the non-resonant behavior of the S factor of the ^(12)C+^(12)C and ^(16)O+^(16)O fusions very well over a wide range of energies.展开更多
文摘Positron annihilation in TiO2 rutile crystal is studied by an assumption that a positron binds with valance electrons of a titanium dioxide to form a pseudo TiO2-positron molecule before it annihilates with these electrons. The orbital modification consisting of explicit electron-positron and electron-electron correlation in each electronic orbital is used for the electrons and positron wave functions. By these wave functions, the calculation results of the positron lifetimes in unmitigated and defective TiO2 crystals are about 170 ps, 266 ps and 243 ps, respectively. These results are in good agreement with experimental data of the positron lifetimes in vacancies of TiO2 from 180 ps to 300 ps.
基金supported,in part,by the National Foundation for Scientific and Technological Development(NAFOSTED Project No.103.04-2017.317)
文摘The nuclear mean-field potential built up during the ^(12)C+^(12)C and ^(16)O+^(16)O collisions at low energies relevant for the carbon-and oxygen-burning processes is constructed within the double-folding model(DFM) using the realistic ground-state densities of^(12)C and^(16)O, and CDM3Yn density-dependent nucleon–nucleon(NN) interaction. The rearrangement term, indicated by the Hugenholtz–van Hove theorem for the single-particle energy in nuclear matter, is properly considered in the DFM calculation. To validate the use of the density-dependent NN interaction at low energies, an adiabatic approximation was suggested for the dinuclear overlap density. The reliability of the nucleus–nucleus potential predicted through this low-energy version of the DFM was tested in the optical model(OM) analysis of the elastic^(12)C+^(12)C and ^(16)O+^(16)O scattering data at energies below 10 MeV/nucleon.These OM results provide a consistently good description of the elastic angular distributions and 90 excitation function. The dinuclear mean-field potential predicted by the DFM is further used to determine the astrophysical S factor of the ^(12)C+^(12)C and ^(16)O+^(16)O fusions in the barrier penetration model. Without any adjustment of the potential strength, our results reproduce the non-resonant behavior of the S factor of the ^(12)C+^(12)C and ^(16)O+^(16)O fusions very well over a wide range of energies.
