Qixue Wu

Hyperfine structure of the 23P state of 3He with and without an external magnetic field

The hyperfine structure of the 23P state of 3He with and without an external magnetic field is precisely calculated. All the linear terms, diamagnetic terms and the α2 relativistic correction terms are included in the Zeeman Hamiltonian. The values of the fields for 32 crossings and 5 anticrossings of the magnetic sublevels are theoretically predicted for magnetic field strengths up to 10 000 gauss. The results are compared with experimental data and other theoretical works. All related matrix elements are calculated with high accuracy by the use of double basis set Hylleraas-type variational wavefunctions.

Hyperfine suppression of 2 {sup 3}S{sub 1} - 3 {sup 3}P{sub J} transitions in {sup 3}He.

Two anomalously weak transitions within the 2(3)S_(1)--3(3)P_(J) manifolds in 3He have been identified. Their transition strengths are measured to be 1000 times weaker than that of the strongest transition in the same group. This dramatic suppression of transition strengths is due to the dominance of the hyperfine interaction over the fine-structure interaction. An alternative selection rule based on IS coupling (where the nuclear spin is first coupled to the total electron spin) is proposed. This provides qualitative understanding of the transition strengths. It is shown that the small deviations from the IS coupling model are fully accounted for by an exact diagonalization of the strongly interacting states.