Improved ^{4}He i 1snl ionization energy, energy levels, and Lamb shifts for 1sns and 1snp terms
Abstract
The consistencies of calculated term values (ionization energies) for various 1snl terms having n=58, l=15 are tested by microwavespectroscopic and other available data. The most accurate n P, n D, and n F term values obtained from published variational calculations are generally found to be consistent, within the estimated uncertainties, with more accurate n G and n H energies from corepolarization theory [R. J. Drachman, Phys. Rev. A 26, 1228 (1982)]. The n ^{3}D and n ^{1}D term values from variational calculations [A. Kono and S. Hattori, Phys. Rev. A 34, 1727 (1986)] are confirmed within uncertainties as small as 10^{4} cm^{1} (n=8), although the ^{1}D values are systematically too large by amounts within the uncertainties. The ionization energy E_{I} has accordingly been reevaluated by using only the calculated n ^{3}D term values (n=4,5) and available experimental measurements: The resulting E_{I} value is 198 310.772 27(40) cm^{1} with respect to the 2 ^{3}S level at 159 856.077 60 cm^{1}. The available data and calculated term energies allow determination of the entire 1snl excited energylevel system with much improved accuracy for the higher levels. Calculated energies are used instead of experimental results in several cases involving apparently underestimated experimental uncertainties. The levels are given explicitly through n=8. Experimental term values based on the new E_{I} value are combined with calculated term values not including QED contributions to obtain ``experimental'' Lamb shifts for a number of n S and n P terms. The experimental Lamb shifts of the 2 ^{3}S_{1}2 ^{3}P_{1} and 2 ^{3}P_{1}2 ^{1}P_{1} separations are also reevaluated. Results of comparisons of these experimental shifts with various calculated Lamb shifts vary from agreement within 0.3% experimental uncertainties (for the 2 ^{3}S shift and shift of the 2 ^{3}S_{1}2 ^{3}P_{1} separation) to relatively large discrepancies for the higher n S terms (~50% for 5 ^{3}S). Twoelectron QED contributions calculated for 2 ^{3}S, 2 ^{1}S, and 2 ^{1}P [G. W. F. Drake and A. J. Makowski, J. Phys. B 18, L103 (1985)] are confirmed within uncertainties of about 35% by the data in each case, the level of confirmation for 2 ^{3}S and 2 ^{1}P being subject to additional uncertainties from asyet uncalculated contributions.
 Publication:

Physical Review A
 Pub Date:
 October 1987
 DOI:
 10.1103/PhysRevA.36.3575
 Bibcode:
 1987PhRvA..36.3575M
 Keywords:

 35.10.Fk;
 35.10.Hn;
 32.30.Jc;
 Visible and ultraviolet spectra