Atomic and molecular structures of positronium, dipositronium and positronium hydride

The three positron based chemical entities, analogous to hydrogen atom, hydrogen molecule and hydride, are drawing increasing attention in the literature. While a lot is known about the binding energies, not much is known about the radii of the atoms and ions and bond lengths and structures of these exotic entities. This article brings for the first time exact values of these structural properties which are comparable with known data. It is hoped that the results will be of help for a better understanding and further development of the chemistry and physics of these exotic compounds and of their possible role as intermediates in chemical and interfacial processes. Subject terms: Chemical physics, Physical chemistry, Atomic physics, Nuclear physics, Structural chemistry N at ur e P re ce di ng s : h dl :1 01 01 /n pr e. 20 11 .6 29 0. 1 : P os te d 26 A ug 2 01 1 2 Positronium (Ps), dipositronium (Ps2) and positronium hydride (PsH), based on positron, an antimatter, have drawn considerable interest in recent literature. To cite a few, see. Several years ago, the author had proposed that, since a neutron (n) and a proton (p) decay by emitting an electron (e) and a positron (e) respectively, an (e e) pair, now known as positronium, could be the intermediate when neutrons and protons fuse together to form atomic nuclei. At distances (ae-e+) of the order of 10 m, the (ee) pair annihilates releasing two gamma photons of energy, mec 2 = 0.511 Mev each. This article brings for the first time the structures of the above exotic chemical entities based on exact atomic radii. It is hoped that the results will be of help for a better understanding and further development of the chemistry and physics of these short lived compounds and of their possible yet undiscovered important role as intermediates in chemical and interfacial processes, nucleosynthesis, and biophysics. Positronium atom, is a positron (e) bound to an electron (e) at a distance of the order of 10 m as in a hydrogen atom, H in which a proton (p) is bound to an electron (e) at the distance of the Bohr radius, aH (~ 0.5 x 10 -10 m). Dipositronium (Ps2) is a molecule consisting of a pair of positronium atoms, like H2 where a pair of (p e) combine to form the molecular hydrogen. Positronium hydride (PsH) is a diatomic molecule, which can be completely or partially covalent or ionic. Considered here are the ionization energy, Bohr radius and bond lengths in the above, based on exact atomic and ionic radii evaluated here for the first time. The observed bond lengths of PsH are comparable with the corresponding sums of the ionic and atomic radii obtained here. The ionization energy, Bohr radius and reduced mass relation for Ps can be considered similar to that for H. The ground state energy, EH = eIH (where IH is the ionization potential and e is the elementary charge), Bohr radius, aH (which is the N at ur e P re ce di ng s : h dl :1 01 01 /n pr e. 20 11 .6 29 0. 1 : P os te d 26 A ug 2 01 1 3 distance between the electron and proton) and the reduced mass, μH,red = me-mp+/(me+ mp+) (where meand mp+ are masses of the electron and proton respectively), are related as follows, EH = (1/2)(e /κaH) = (1/2)μH,red(αc) = eIH (1a-c) where, κ = 4πε0, the atomic unit of permittivity, ε0, the electric constant, α, the fine structure constant, h, the Planck constant and c, the speed of light in vacuum. On using the latest values, of the physical constants, it follows that μH,red = 0.910442 x 10 -31 kg (2) EH = (1/2)μH,red(αc) = 2.178686 x 10 J (3) IH = EH/e = 13.5983 V (4) aH = (1/2)(e/κIH) = 0.5295 x 10 m = 0.05295 nm. (5) Bohr radius (aH) was shown to be the sum of two Golden sections aH,eand aH,p+ pertaining to the electron and proton: In equation (1c), IH = (Ip+ + Ie-)/2 where Ip = e/(κaH,p+) and Ie= -e/(κaH,e-) are the components of the ionization potential, and aH,eand aH,p+, are sections of aH pertaining to (p ) and (e) respectively. Thus, IH = (1/2)(e/κaH) = (1/2)(e/κ)[(1/aH,p+) (1/aH,e-)] (6a,b) 1/aH = (1/aH,p+) (1/aH,e-); aH = aH,e+ aH,p+ (7a,b) (aH,e-/aH,p+) 2 (aH,e-/aH,p+) = 1 (8) N at ur e P re ce di ng s : h dl :1 01 01 /n pr e. 20 11 .6 29 0. 1 : P os te d 26 A ug 2 01 1