Theory and computation of triply excited resonances: Application to states ofHe−

Abstract

Autoionizing multiply excited states offer unusual challenges to the theory of electronic structure and spectra because of the presence of strong electron correlations, of their occasional weak binding, of their proximity to more than one threshold, and of their degeneracy with many continua. Here we discuss a theory that addresses these difFiculties in conjunction with the computation of their wave functions and intrinsic properties. Emphasis is given on the justification of the possible presence of self-consistently obtained open-channel-like (OCL) correlating configurations in the square-integrable representation of such states and on their effect on the energy E and the width I . Application of the theory has allowed the prediction of two hitherto unknown He triply excited resonances, the 2s2p P (E=59.71 eV, above the He ground state, I =79 meV) and the 2p D' (E=59.46 eV, I =282 meV) (1 a.u. =27.2116 eV).These resonances are above the singly excited states of He and are embedded in its doubly excited spectrum. The relatively broad 2p D' state interacts strongly with the He 2s2p P' ed continuum. The effect of this interaction has been studied in terms of the coupling with fixed core scattering states as well as with a self-consistently computed OCL bound configuration. The position of the He 2p' D' resonance is below that of the He 2p 'D autoionizing state at 59.91 eV and of the He 2p P bound state at 59.68 eV. The partial decay widths to the three important open channels are y(2s2p P')=252 meV, y(1s2p 'P')=21 meV, y(1s2p 'P')=9 meV. The final core states are also represented by correlated (multiconfigurational Hartree-Fock) functions. The 2s2p P state couples to four neighboring He thresholds, the 2s2p P', 2p P, 'D, and 2s2p 'P'. It is above the He 2s2p P' threshold at 58.31 eV, with respect to which it is a valence shape resonance, and below the He 2p 'D and 2s2p 'P' autoionizing states. In the limit of an exact energy calculation, we suggest that its position would also come below that of the 2p P state, which it overlaps. Its partial widths are y(2s2p P') =60 meV, y(1s2p P') =9 meV, y(1s2p 'P') =10 meV. The present results, considered together with published ones on other n=2 intrashell states, show that the recently measured [R. N. Gosselin and P. Marmet, Phys. Rev. A 41, 1335] closely lying structures at 58.415 and 58.48 eV cannot correspond to the He 2p S' and D' states, as these authors proposed.PACS number(s): 31.50.+w, 31.20.Tz, 32.80.Dz, 34.80.Dp

Radiative lifetimes of triply excited states of the Li isoelectronic sequence

“…Of course, improvement of our results by inclusion of additional localized correlation is straightforward (e.g. , [17]). Nevertheless, it was considered unnecessary for the practical purposes of the present work which aimed at economically producing a large number of energy differences and of transition probabilities for wave functions computed at approximately the same level of accuracy involving hitherto unexplored states in ions.…”

“…Therefore, for the ab initio computation of a large number of data involving such states, it is necessary for the theoretical approach not only to be properly justified but also to combine physically meaningful accuracy with economy. The computations herein are based on the state-specific approach ( [16,17], and references therein), which starts with a multiconfigurational Hartree-Fock (MCHF) wave function consisting of properly selected few configurations and continues, if necessary by the requirements of the problem, with the inclusion of the remaining localized and asymptotic multichannel correlation. In this way it is possible to obtain efficiently properties of a variety of polyelectronic highly excited states and not of just specialized cases of two-or three-electron systems.…”

“…The first was obtained by the numerical MCHF method [18]. The justification of such computations for states embedded in the continuum is discussed in [16,17]. These (Table IV).…”

Regular series of doubly excited states inside two-electron continua: Application to2s2-hole states in neon above the Ne2+

“…One of the advantages of the state-specific calculation of MCHF is that this wave function accounts in an efficient way for the self-consistently adjusting major correlations that contribute to localization, including a few that incorporate parts of the open-channel continuous spectrum, which we have named the open-channel-like (OCL) configurations [23][24][25]. In the work of this paper, such OCL configurations have been eliminated via appropriate transformations.…”

“…Related discussions can be found in Refs. [11,[23][24][25]. These techniques were applied in the present paper when necessary in addition to ones specific to the problem-see Sec.…”