Xw. Zhu et Kt. Chung, ENERGIES AND FINE-STRUCTURES OF 1S(2) 2SNP (N=2,3) P-1(O) AND P-3(2,1,0)O STATES OF BE-LIKE IONS, Physical review. A, 50(5), 1994, pp. 3818-3826
The energies and wave functions of the Be-like 1s(2)2snp (n=2,3) P-1(o
) and P-3(2,1,0)o, states are calculated with a full-core plus correla
tion. method for ions from B II to Ne VII, Mg IX, and Si XI. The relat
ivistic corrections and fine structures are calculated with the first-
order perturbation theory. Higher-order effects are estimated. The cal
culated excitation energies (relative to the 1s(2)2s(2) ground state)
are compared with the experiment. Intermediate coupling between the P-
3(1)o and P-1(1)o states is also considered. Most of the predicted P-3
(J)o energies agree with the experiment to within a few cm(-1). The fi
ne-structure splittings of the 1s(2)2s2p(3)P(2,1,0)(o) states calculat
ed in this work all agree with the best experimental data in the liter
ature. Our results show that for systems of Z greater than or equal to
9, it is critically important to consider intermediate coupling. For
Si XI, it shifts the 2s2p(3,1)P(1)(o) levels by 86 cm(-1) and the 2s3p
(3,1)P(1)(o) energies by 193 cm(-1). The predicted 2s2p(1)P(o) energie
s are slightly higher than the experimental data; the discrepancy incr
eases from 14 cm(-1) for Z=5 to 93 cm(-1) for Z=14.