Primary retention following nuclear recoil in p-decay: Proposed synthesis of a metastable rare gas oxide (38ArO4) from (38C1O4~~) and the evolution of chemical bonding over the nuclear transmutation reaction path

摘要

Argon tetroxide (ArO4) is the last member of the N=50 e~ isoelectronic and isosteric series of ions; SiO44~, P043", SQ42~, and C1O4~. A high level computational study demonstrated that while ArO4 is kinetically stable it has a considerable positive enthalpy of formation (of ~298 kcal/mol) (Lindh et al, 1999. J. Phys. Chem. A 103, pp. 8295-8302) confirming earlier predictions by Pyykko (1990. Phys. Scr. 33, pp. 52-53). ArO4 can be expected to be difficult to synthesize by traditional chemistry due to its metastability and has not yet been synthesized at the time of writing. A computational investigation of the changes in the chemical bonding of chlorate (C104~) when the central chlorine atom undergoes a nuclear transmutation from the unstable artificial chlorine isotope 38C1 to the stable rare argon isotope 38Ar through p-decay, hence potentially leading to the formation of ArO4, is reported. A mathematical model is presented that allows for the prediction of yields following the recoil of a nucleus upon ejecting a p-electron. It is demonstrated that below a critical angle between the ejected p-electron and that of the accompanying antineutrino their respective linear momentums can cancel to such an extent as imparting a recoil to the daughter atom insufficient for breaking the Ar-0 bond. As a result, a primary retention yield of ~1% of ArO4 is predicted following the nuclear disintegration. The study is conducted at the quadratic configuration interaction with single and double excitations [QCISD/6-311+G(3d/)] level of theory followed by an analysis of the electron density by the quantum theory of atoms in molecules (QTAIM). Crossed potential energy surfaces (PES) were used to construct a PES from the metastable ArO4 ground singlet state to the Ar-0 bond dissociation product ArO3+O(3P) from which the predicted barrier to dissociation is ca. 22 kcal/mol and the exothermic reaction energy is ca. 28 kcal/mol [(U)MP2/6-3U+G(d)].