We carry out the first time-resolved measurement of Rb atoms desorbing from octadecyltrichlorosilane coated sur- faces by polarizing the atoms near the surface using an evanescent wave pump pulse and watching the subs...We carry out the first time-resolved measurement of Rb atoms desorbing from octadecyltrichlorosilane coated sur- faces by polarizing the atoms near the surface using an evanescent wave pump pulse and watching the subsequent intensity change of another evanescent wave probe beam, and find the mean adsorption （dwell） time to be about 400ns at a cell body temperature of 112℃. The adsorption energy is found to be 0.19eV from the surface tem- perature dependence of the adsorption time. This method can be extended to study the adsorption/desorption process of other alkali atoms on other surfaces of transparent substrates with an ultimate time resolution limited by the flight time of atoms in the evanescent wave which is of the order of nanoseconds.展开更多
Production of positron-electron (e^(+) e^(-) ) pairs in an intense laser pulse is investigated by solving the Dirac equation with analytical and numerical methods.We observe that the probability of the pair production...Production of positron-electron (e^(+) e^(-) ) pairs in an intense laser pulse is investigated by solving the Dirac equation with analytical and numerical methods.We observe that the probability of the pair production will firstly decrease slowly as the pulse length T becomes shortened.Then it will increase until T is reduced to the Compton time Tc =(h)/(mec) ≈ 1.29 × 10^(-21)s and finally decrease exponentially to zero.Hence,for a prominent pair production,we not only require that the electric field strength should be higher than the Schwinger critical value Ecr =m^(2)c^(3)/(e(h)) ≈ 1.32 × 10^(16) V/cm,but also that the pulse duration T should be larger than Tc.The latter is shown to be related to momentum requirement for the transition.For fields with different pulse lengths,the phase and chirp influences upon the pair production are also explored.展开更多
The momentum and isospin dependence of symmetry potential and effective mass in isospin asymmetric nuclear matter is investigated in the framework of the Brueckner-Hartree-Fock approach by adopting the realistic Bonn ...The momentum and isospin dependence of symmetry potential and effective mass in isospin asymmetric nuclear matter is investigated in the framework of the Brueckner-Hartree-Fock approach by adopting the realistic Bonn B two-body interaction in combination with a consistent microscopic three-body force.It is demonstrated that symmetry potentials at the normal density for different asymmetry parameters are in good agreement with the empirical value constrained by the experimental data,and the neutron and proton effective masses show strong isospin splitting with m*n > m*p on the whole range of asymmetry parameters.In the end,the density dependence of the Landau mass is displayed.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 11074050
文摘We carry out the first time-resolved measurement of Rb atoms desorbing from octadecyltrichlorosilane coated sur- faces by polarizing the atoms near the surface using an evanescent wave pump pulse and watching the subsequent intensity change of another evanescent wave probe beam, and find the mean adsorption （dwell） time to be about 400ns at a cell body temperature of 112℃. The adsorption energy is found to be 0.19eV from the surface tem- perature dependence of the adsorption time. This method can be extended to study the adsorption/desorption process of other alkali atoms on other surfaces of transparent substrates with an ultimate time resolution limited by the flight time of atoms in the evanescent wave which is of the order of nanoseconds.
基金Supported by the National Natural Science Foundation of China under Grant No 10974056 and 10975036Shanghai Pujiang Talent Project under Grant No 07pj14036.
文摘Production of positron-electron (e^(+) e^(-) ) pairs in an intense laser pulse is investigated by solving the Dirac equation with analytical and numerical methods.We observe that the probability of the pair production will firstly decrease slowly as the pulse length T becomes shortened.Then it will increase until T is reduced to the Compton time Tc =(h)/(mec) ≈ 1.29 × 10^(-21)s and finally decrease exponentially to zero.Hence,for a prominent pair production,we not only require that the electric field strength should be higher than the Schwinger critical value Ecr =m^(2)c^(3)/(e(h)) ≈ 1.32 × 10^(16) V/cm,but also that the pulse duration T should be larger than Tc.The latter is shown to be related to momentum requirement for the transition.For fields with different pulse lengths,the phase and chirp influences upon the pair production are also explored.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11075037,11175219 and 10875151the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry+1 种基金the Fundamental Research Funds for the Central Universities of China,Shanghai Leading Academic Discipline Project(B107)the Knowledge Innovation Project of Chinese Academy of Sciences(KJCX2-EW-N01).
文摘The momentum and isospin dependence of symmetry potential and effective mass in isospin asymmetric nuclear matter is investigated in the framework of the Brueckner-Hartree-Fock approach by adopting the realistic Bonn B two-body interaction in combination with a consistent microscopic three-body force.It is demonstrated that symmetry potentials at the normal density for different asymmetry parameters are in good agreement with the empirical value constrained by the experimental data,and the neutron and proton effective masses show strong isospin splitting with m*n > m*p on the whole range of asymmetry parameters.In the end,the density dependence of the Landau mass is displayed.
