https://doi.org/10.1140/epjd/e2014-40734-2
Regular Article
Quantum Monte Carlo and high-level ab initio molecular orbital investigation of dissociation channels of the positronic alkali-metal hydrides, [XH;e+] (X = Li, Na, and K)*
1
Quantum Chemistry Division, Yokohama City
University, Seto 22-2, Kanazawa-ku,
236-0027
Yokohama,
Japan
2
TCM Group, Cavendish Laboratory, University of
Cambridge, J J Thomson
Avenue, Cambridge,
CB3 0HE,
UK
a
e-mail: ykita@yokohama-cu.ac.jp
Received: 21 November 2013
Received in final form: 21 January 2014
Published online: 21 March 2014
Energy thresholds for dissociation channels of positronic alkali-metal hydrides, [XH;e+] (X = Li, Na, and K), to XH + e+(positron dissociation), XH+ + Ps (positronium dissociation), and X+ + [H−;e+] (positronic hydride ion dissociation) have been calculated using quantum Monte Carlo and high-level ab initio molecular orbital methods, and including quantum zero-point vibrational energy of all of the particles. As the atomic number of X increases from Li to K, the dissociation energy to XH + e+ increases because the dipole moment of XH increases with the atomic number of X, while the dissociation energy to XH+ + Ps decreases. The energy threshold for the ionic dissociation to X+ + [H−;e+] is also reduced, and we obtain 0.975 (3) eV, 0.573 (12) eV, and 0.472 (19) eV for [LiH;e+], [NaH;e+], and [KH;e+], respectively, for this channel. Our results strongly support the conclusion that, among these three channels, the lowest energy dissociation for [XH;e+] is the pathway to X+ + [H−;e+], where X = Li, Na, and K.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2014