Theoretical Investigation On Hyperfine Structure Properties Of Cesium And Cesium-like Systems

The hyperfine interaction is caused by the interaction between the nuclear electromagneticmultipole moment and the electron.Accurate knowledge of the hyperfine-structure information of atomic system is very importance in many applications involving precise spectroscopy,atomic clocks,quantum information,and laser cooling and trapping.In this dissertation,we use the relativistic many-body method to calculate the hyperfine-structure properties of Cs and Cs-like system.Combining with the high-precise measured results,we determine the nuclear electromagnetic multipole moments.Hyperfine interaction is a short-range property,which is sensitive with the relativistic effect and electron-electron correlation correction.Therefore,we also investigate the electron correlation correction trends of hyperfine interaction in Cs and Cs-like system.The details are following”(1)The energy,hyperfine-structure constant A,B,and C of the 6s_1/2?6p_1/2?6p_3/2?5d_3/2and 5d_5/2 states in Cs are calculated by relativistic many-body perturbation theory,relativistic coupled-cluster theory with and without the non-linear terms.The dependence of hyperfine-structure constant A and energy properties on basis function is studied by comparing B-spline and Gauss basis set.The electron correlation correction is also investigated by relativistic many-body method at the different levels.Combining the measured and calculated values of the 6p_3/2hyperfine-structure constants,we determine the electron quadrupole moment Q and the magnetic octupole?,and compare with available matrix elements resulted from the second-order hyperfine-structure interaction.(2)Like Cs,we calculated energy and hyperfine-structure constants of the first five states of ^135,137Ba⁺using relativistic many-body methods.Combining the measured and calculated values,we determined the nuclear electromagnetic multipole moments of ^135,137Ba nuclear.Our recommended results of magnetic dipole moments are in agreement with the measured values,but the Q is smaller then the measured one about 3%.The difference about 10%among all available theoretical magnetic octupole?can be found.We find that the correlation correction trend of Ba⁺and Cs are the same.(3)La²⁺is a Cs-like ionic system,but it have different level order from Cs and Ba⁺,with the ground state 5d_3/2.We present an ab initio calculations of the magnetic-dipole and electron-quadrupole HFS constants of 24 low-lying states of La²⁺by using relativistic coupled-cluster method with single and double excitation approximation.Our CCSD results for the magneticdipole HFS constants of 5d_3/2and 4f_5/2,7/2states are consistent with recently measured values by using optogalvanic spectroscopy within 3%,but a large deviation for electron-quadrupole HFS constants are observed.In addition,we also investigate electron correlation trends in the evaluation of HFS constants of the aforementioned states.We observed the general correlation trends for HFS constant A of S and P states are the same as the case of Cs atom,but other states are different.We also found that the 5d_5/2state has a large electron correlation effect and has a strong cancellation with the zero-order Dirac Fock value.