Hyperfine-induced effects on the linear polarization of the magnetic-quadrupole lines of spin-1/2 Be-like ions excited by electron impact

The linear polarization of magnetic-quadrupole emission lines 1s(2)2s2p(3/2) P-3(2) -> 1s(2)2s(2 1) S-0 and 1s2s(2)2p(3/2) P-3(2) -> 1s(2)2s(2 1) S-0 following electron-impact excitation of Be-like ions with nuclear spin I = 1/2 is studied by employing the density-matrix theory and the relativistic distorted-wave theory. To explore the effects of the hyperfine interaction, detailed calculations are performed for the polarization of the magnetic-quadrupole lines emitted from Xe-A(50+) (A = 125, 127, and 129) and Tl-A(77+) (A = 187, 205, and 207) ions with different nuclear magnetic dipole moments mu(I) at a series of impact electron energies. It is shown that the hyperfine interaction strongly lowers the polarization of the 1s(2)2s2p(3/2) P-3(2) -> S-1(0) line at all considered impact energies, while its effects behave less and less prominent with increasing impact energy for the 1s(2)2s(2)p(3/2) P-3(2) -> S-1(0) line. In addition, we also find that the polarization of the 1s(2)2s2p(3/2) P-3(2) -> S-1(0) line is much more sensitive to mu(I) than that of the 1s(2)2s2p(3/2) P-3(2) -> S-1(0) line. In particular, for the 1s(2)2s2p(3/2) P-3(2) -> S-1(0) line of spin-1/2 Xe50+ ions, the differences in the polarization among the isotopes are significant. These findings indicate that precise polarization measurements of magnetic-quadrupole lines of Be-like ions are expected to be used for exploring the hyperfine interaction and even the nuclear magnetic dipole moment of nonzero-spin isotopes.

Automated summary

This study investigates the linear polarization of magnetic-quadrupole emission lines of Be-like ions with nuclear spin through the use of density-matrix theory and relativistic distorted-wave theory. The effects of hyperfine interaction and different nuclear magnetic dipole moments on the polarization of these lines are explored. The findings suggest that precise polarization measurements of magnetic-quadrupole lines could be used to study the hyperfine interaction and nuclear magnetic dipole moment of isotopes with nonzero spins.