Positron binding to alkali-metal hydrides: The role of molecular vibrations

Abstract

The bound vibrational levels for J = 0 have been computed for the series of alkali-metal hydride molecules from LiH to RbH, including NaH and KH. For all four molecules the corresponding potential-energy curves have been obtained for each isolated species and for its positron-bound complex ͑e + XH͒. It is found that the calculated positron affinity values strongly depend on the molecular vibrational state for which they are obtained and invariably increase as the molecular vibrational energy content increases. The consequences of our findings on the likelihood of possibly detecting such weakly bound species are briefly discussed.

The quantum theory of atoms in positronic molecules: A case study on diatomic species

“…In all positronic species except for CN À ,e þ (and to some extent OH À ,e þ ) the position is exclusively contained in a single quantum atom, the one that is more electronegative. This pattern is in line with the results of previous studies, which have considered the 2D positronic distribution maps for various species [40,41,44,49,[52][53][54]58]. The only serious deviation is observed in the case of CN À ,e þ in which both quantum atoms contain comparable populations ($0.3 in carbon versus $0.7 in nitrogen basins).…”

Positron attachment to theH2(A3Mitroy1, Zhang2 2011Phys. Rev. A5030View full textAdd to dashboardCite

“…since such conditions are known to promote positron attachment [1,19]. The significance of this point has not received much attention in existing works that investigate positron binding to molecules [9][10][11][12][13][14]. Such a strategy could be usefully applied to other molecules to guide a search aimed at identifying electronically excited states capable of attaching a positron into a Feshbach resonance.…”

“…The only molecule for which precise estimates of the positron binding energy are known is the e + LiH system [5][6][7][8]. There have been calculations of positron binding to a number of other molecules [9][10][11][12][13][14] but the accuracy obtained for these systems is relatively low.…”

Configuration interaction calculations of annihilation rates for positronic complexes of alkali hydrides

“…Applications have been carried out for the series of alkali hydrides [3][4][5] as well as a number of alkali oxides [6,7]. This work has shown that accurate potential curves can be obtained at the conventional (molecular) CI level, but also that the amount of the correlation energy itself is underestimated by a significant margin at this level of treatment.…”

“…This is the main reason why high-l basis functions are required to obtain high accuracy in such calculations [8], since without them it is impossible to obtain a quantitative description of the positron's charge distribution in the neighborhood of each atomic nucleus and its inner shells. However, there is strong evidence to indicate that the missing correlation effects are predominantly atomic in [3][4][5][6][7]. The primary success of the MRD-CI calculations is that, when calculating potential energy curves for positron-molecule complexes without such high-l basis functions, atomic-like correlation effects are underestimated by nearly the same amount over the entire range of bond distance considered.…”