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Journal of Physics B Atomic Molecular and Optical Physics

The stability and structure of Li+Ps2and Na+Ps2

Jim Mitroy, G Ryzhikh

Published Oct 25, 1999• 35 citations
Publisher

Abstract

The fixed-core stochastic variational method has been used to demonstrate the existence of an electronically stable ground state for the Li + Ps 2 and Na + Ps 2 systems. The stability of Li + Ps 2 has been indicated previously in an ab initio calculation by Varga, but the present estimate of the binding energy is much closer to convergence. The Li + Ps 2 system has a binding energy of 0.013 149 Hartree and a 2 annihilation rate of 3.86 × 10 9 s -1 . The Na + Ps 2 system has a binding energy of 0.005 736 Hartree and an annihilation rate of 4.02 × 10 9 s -1 . Examination of the interparticle expectation values, correlation functions and the annihilation rates suggests that both of these systems can be best described as a Ps 2 molecule weakly bound to an alkali atom cation.

DOI
10.1088/0953-4075/32/21/102

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The fixed-core stochastic variational method has been used to demonstrate the existence of an electronically stable ground state for the Li + Ps 2 and Na + Ps 2 systems. The stability of Li + Ps 2 has been indicated previously in an ab initio calculation by Varga, but the present estimate of the binding energy is much closer to convergence. The Li + Ps 2 system has a binding energy of 0.013 149 Hartree and a 2 annihilation rate of 3.86 × 10 9 s -1 . The Na + Ps 2 system has a binding energy of 0.005 736 Hartree and an annihilation rate of 4.02 × 10 9 s -1 . Examination of the interparticle expectation values, correlation functions and the annihilation rates suggests that both of these systems can be best described as a Ps 2 molecule weakly bound to an alkali atom cation.
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We calculate the binding energy and geometry of the weakly bound e(+)Li and e(+)Na systems within the framework of hyperspherical coordinates. The Schrodinger equation in hyperangular coordinates is solved at a series of fixed hyper-radii using B-splines and the resulting coupled hyper-radial equation is solved using the slow variable discretization method developed by Tolstikhin et al. [J. Phys. B 29, L389 (1996)]. Great efforts are made in optimizing the distribution of B-splines to overcome the slow convergence of the binding energy and geometrical quantities. This approach allows us to obtain the results with improved convergence that are in good agreement with the best values reported to date. In addition, an analysis of the structure of the two systems is also made and the e(+)Na system is seen to exhibit quantum halo features.
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