Accurate long-range coefficients for two excited like isotope He atoms:He(2P1)–He(2

Abstract

A general formalism is used to express the long-range potential energies in inverse powers of the separation distance between two like atomic or molecular systems with P symmetries. The long-range molecular interaction coefficients are calculated for the molecular symmetries ⌬, ⌸, and ⌺, arising from the following interactions: He͑2 1 P͒ -He͑2 1 P͒, He͑2 1 P͒ -He͑2 3 P͒, and He͑2 3 P͒ -He͑2 3 P͒. The electric quadrupolequadrupole term C 5 , the van der Waals ͑dispersion͒ term C 6 , and higher-order terms C 8 and C 10 are calculated ab initio using accurate variational wave functions in Hylleraas coordinates with finite nuclear mass effects. A comparison is made with previously published results where available.

Theory and applications of atomic and ionic polarizabilities

“…6860( 25) [362] Better information about the specific values of the dispersion coefficients for many atoms has become available primarily because of the importance of such data for the field of cold-atom physics. There have been the near exact non-relativistic calculation by Yan and co-workers on H, He and Li using Hylleraas basis sets [117,118,[365][366][367][368][369]. An important series of calculations on the ground and excited states of the alkali atoms were reported by Marinescu and co-workers [358,[370][371][372][373].…”

Long-range interactions between excited helium and alkali-metal atoms

“…They are then used to calculate the dispersion coefficients by summing over intermediate states represented by atomic physical states and pseudostates. For atomic He and Li the energy spectra and reduced matrix elements of the multipole transition operators are the same as those used for calculating the dispersion coefficients for the low-lying states of He and Li [25][26][27][28][29][30][31]. They were calculated using Hylleraas basis functions.…”

“…In conclusion, dispersion coefficients have been calculated for the long-range interaction of the first four excited states of He, i.e., He(2 1,3 S) and He(2 1,3 P ), with the low-lying states of the alkali-metal atoms Li, Na, K, and Rb by summing over the reduced matrix elements of the multipole transition operators [22][23][24]. For He and Li atoms the reduced matrix elements have been previously generated with Hylleraas-type basis functions [25][26][27][28][29][30][31]. For the alkali-metal atoms the transition arrays of the valence electrons have been previously computed by the CICP method, where the effect of core excitations has been taken into account by approximately constructing the oscillator strength distributions of the atomic cores [24,[32][33][34][35][36][37].…”

Long-range interactions of excited He atoms with ground-state noble-gas atoms

“…For He, the energy spectra and reduced matrix elements of the multipole transition operators are the same as those used for calculating the dispersion coefficients for the low-lying states [19][20][21][22][23][24] and the polarizabilities of Rydberg states [25]. The wave functions are expanded in terms of Hylleraas-type basis functions,…”