THE DISSOCIATIN ENERGY OF THE HYDROGEN MOPLECULE
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Date
1992
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
Fluorescence-excitation spectroscopy has been used to measure the threshold for the second dissociation limit of $H_{2}(B^{\prime}^{1}\Sigma{_{u}}^{\prime}) = H (1s) + H (2s)$ at $118 377.06 \pm 0.04 cm^{-1}$, and to determine a precise value for the dissociation energy of the ground electronic state. Coherent radiation near 84.5nm was used to excite a beam of hydrogen gas, and tuned over this threshold region. Metastable 2s atoms formed in the dissociation process were detected by quenching with an electric field, delayed -- 200 ns after the excitation pulse. This delay time was sufficient to allow molecules excited in the B and B^{\prime} states to decay by radiation, long before the 2s atoms were quenched to produce Lyman-$\alpha$ radiation. This it was possible to observe the dissociation limit clearly, without overlapping molecular features, and to derive a value for the dissociation energy of $H_{2}$, namely, $D_{o} (H_{2}) = 36 118.11 \pm 0.08 cm^{-1}$. This is in good agreement with the latest theoretical $value^{1}$ of $36 118.09\pm 0.10 cm^{-1}$, which includes nonadiabatic, relativistic, and radiative corrections. When the present value is combined with recent experimental values of the ionization potentials of H and $H_{2}$ it yields $D_{0}$ ($H_{2}^{+})=21 379.36 \pm 0.08 cm^{-1}$, also in good agreement with theory.
Description
$^{1}$ W. Kolos, K. Szalewicz, and H.J. Monkhorst, J. Chem. Phys. 84, 3278 (1986).
Author Institution: Department of Physics, University of Toronto; D\'{e}partment de Physique Atomique et Moleculaire, Universit\'{e} de Rennes I, 35042 Rennes, France
Author Institution: Department of Physics, University of Toronto; D\'{e}partment de Physique Atomique et Moleculaire, Universit\'{e} de Rennes I, 35042 Rennes, France