Manifestation of nonuniformity in the electron charge distribution in H 2 + molecular ions colliding with each o
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Manifestation of Nonuniformity + in the Electron Charge Distribution in H2 Molecular Ions Colliding with Each Other G. V. Sholin, A. E. Trenin, V. A. Belyaev, M. M. Dubrovin, and A. A. Terent’ev Russian Research Centre Kurchatov Institute, pl. Akademika Kurchatova 1, Moscow, 123182 Russia e-mail: [email protected] Received July 20, 2006 +
+
Abstract—The anomalous character of threshold properties in the ion–molecule reactions H 2 + H 2 +
+
+
H 3 + p and H 2 + H 2
H + p + H + p has been theoretically analyzed. It has been shown that these reactions ++
+
proceed through the formation of the intermediate H 4 complex. Molecules H 2 in the collision process are described by a chemical model, where the positive charge is concentrated in one of the nuclei. The calculations of the reaction cross sections are in good agreement with the experimental data. It has been shown that the +
chemical model of the H 2 molecule can be consistently explained only in terms of dynamic interactions, i.e., polarization forces and van der Waals forces. PACS numbers: 31.10.+z, 52.20.Hv DOI: 10.1134/S1063776107020057
1. INTRODUCTION Investigation of the features of ion–molecule reac+ tions accompanying collisions of H 2 ions for energies close to the dissociation energy is both of applied importance associated with the problems of increasing the efficiency of gas-discharge sources of proton beams and of fundamental importance, because many important concepts of the quantum theory of molecules can + be verified for the simplest structure, H 2 ion, in these reactions. Moreover, these investigations are also of high interest for studying chemical reactions in interstellar matter. Experimental investigations of the electron-volt range of collision energies of the ion–molecule reactions ⎧ H2 + H + p – 2.65 eV, ⎪ – 5.30 eV, ⎪H + p + H + p ⎨ – 0.82 eV, ⎪ H2 + p + p ⎪ + +3.18 eV, ⎩ H3 + p +
+
+
H2 + H2
and thereby to attribute the exchange of electrons between the nuclei with the excitation of vibrational motion. Indeed, two significantly different approaches to the description of the electron distribution in molecules exist in the current theory of the molecular structure. The traditional quantum-mechanical approach [1] implies the use of ab initio antisymmetric molecular orbitals. In this case, for example, the coordinate wave+
(1) (2)
function in the H 2 molecule is symmetric with respect to the permutation of the nuclei and half the electron charge fits to each nucleus at any time. At the same time, investigation of electron-excited and excimer molecules showed that the best result was achieved by using only those basic orbitals that can be formed when the nuclei of the molecules are spaced at infinite distance. In other words, atoms entering into molecular structures should not change their properties radically.
(3)
In particular, in molecular ions such as H 2 , H 3 , and
(4)
H 3 , etc., the uniform distribution of the electron density throughout all nuclei does not occur, whereas the transition of the electr
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