Theoretical Study Of Long-range Interactions Between Alkali-metal And Rare-gas Atoms

Long-range interactions between atoms play an important role in low-energy,low-temperature collisions,such as ultracold collisions,ultra-cold photoassociation spectra,Bose-Einstein condensations(BEC)etc.In the ultra-cold environment,long-range interactions between atoms have a long time and a wide range,which makes the long range interaction become more important.For example,the structure and stability of BEC depends on the sign and magnitude of the scattering length,and the scattering length depends on the precise values of the dispersion coefficients in the long-range potential.Due to the successful achievement of BEC in hydrogen,alkali metal systems,the theoretical and experimental study of long-range interaction coefficients of alkali metals have attracted more and more attention.There are some theoretical results of the long-range dispersion coefficients between alkali metals and rare gas atoms in non-relativistic cases,however,the theoretical results between the excited states of alkali metal atoms and the rare gas atom is very scarce.In this work,the energy level,oscillator strengths and static polarizability of alkali metal atoms are calculated by using the relativistic configuration interaction plus core polarization(RCICP)method in detail.The long-range dispersion coefficients between ground state and excited states of alkali metal atoms and ground state of rare gases atoms are analyzed intensively.The influence of spin orbit interaction on the long range interaction coefficients is studied.In this thesis,the main significance and progress of long-range dispersion coefficients are introduced in the first chapter.In the second chapter,the RCICP method for calculating atomic structure parameters and the detailed calculated process of long-range dispersion coefficient are introduced.In the third and fourth chapters,the results of this work are discussed in detail.The main research contents are as follows:1.The atomic parameters such as the energy levels,electric multipole(electric dipole,quadrupole,and octupole)oscillator strengths of the alkali metal atoms are calculated by using the RCICP method and program.The electric multipoles(electric dipole,quadrupole,and octupole)static polarizabilities of ground state and low-lying states of the alkali metal atoms are given,and compared with relevant theoretical and experimental results.The rare gas oscillator strength distributions are derived by usingcalculations of rare-gas polarizabilities and dispersion coefficients to tune HartreeFock single-particle energies and expectation values.2.The long-range dispersion coefficients C6,C8,C10 between ground state ns,and low-lying excited states(npj,(n + 1)s,ndj)of the alkali metal atoms(Li,Na,K,Rb,Cs)and the ground state 1S0 of the rare gas atoms are calculated and compared with other theoretical results.At the same time,The influence of relativistic effect(including spin-orbit coupled)on the long-range interaction between alkali metal and rare gas is also analyzed.