Energy levels and spectrum of neutral helium (4He I)

Abstract

A ta bl e of energy levels ba cd on t he most acc ura te obser vation s now availa ble is give n ro r t he neut ral 'H e a tom . Th e wa vele ngths co n ta ined in a rev ised list of 'He I lin es from 320 A to 21132 A are a lso ba sed on t he best meas ure ments, over ha lf of t hem ha ving bee n ca l c ulit~ed from t he wave number se p a rat i o n~ of a ppropri ate levels. Severa l previollsly disturbin g features of t he ' H e term scheme a rc obv iated by t he rev ised level valu es . In it dj s c u s~i o n of t he ex peri me ntal res ults for t his spect rum some compariso ns wi t h t heor y a re m a cl e.

Observation of Atomiclike Electronic Excitations in PureH3eandHHaeften1, Laarmann2, Wabnitz3 et al. 2001Phys. Rev. Lett.377490View full textAdd to dashboardCite

“…4). These bands are attributed to perturbed atomic singlet states according to the energetic position of the free atom 3s, 3d, and 3p states [21]. If our assignment is correct, it is expected that the energetic position of the 3p band depends on the average Wigner-Seitz radius, similar to the 2p features.…”

Variational calculation for the doubly excited state(2p2)Pe3of helium

“…In order to compare with the experiment, we use the well known experimental [15] line with wave number 169 087.01± 0.15 cm −1 corresponding to the transition ͑1s2p͒ 3 P 0 → 1s 2 ͑ 1 S͒. Adding the wave number of the above two lines, an experimental value of 481 301.53± 0.98 cm −1 for the energy of the doubly excited ͑2p 2 ͒ 3 P e term relative to the ground ͑1s 2 ͒ 1 S results.…”

Oscillator strengths for the helium isoelectronic sequence

“…The configuration interaction method follows the same general procedure outlined above, choosing the trial function to I?e a linear expansion as in (2). The two-electron basis, however, consists of produc ts of one-electron functions (orbitals), of the general form…”

“…The trial fun c tion s are take n to be linear ex pan sion s of th e form , (2) The en are linear variational parameters , and the twoelectron basis functions, ¢n, are of the usual Hylleraas variety, with p= (,r, and where (, and x are arlditional nonlinear parameters, Yin is the spherical harmonic appropriate for the desired angular momentum state, and the + and -signs refer to the singlet and triplet states, respectively. Since the spin functions factor out in the two-electron problem, all spin dependence has been suppressed.…”

“…While the s pectra of ne utral helium and sin gly ionized lithium have been stuaied quite thoroughl y [1,2],1 the data available for the rest of thi s isoelectroni c sequence leaves muc h to be desired. Be III , for in!!…”