Effect of Nuclear Electric Quadrupole Moment on the Energy Levels of a Diatomic Molecule in a Magnetic Field. Part I. Heteronuclear Molecules

Abstract

The energy levels of a diatomic molecule---in which one nucleus has electric quadrupole moment and the second zero spin---are derived in "weak" and "strong" magnetic fields, and for intermediate fields in the special case of nuclear spin 1. The calculations are made for large molecular rotational quantum number. The transitions which would be induced in a molecular beam resonance experiment are discussed: Formulae are given for the energy differences involved in these transitions, and the shape of the molecular beam resonance spectrum, corresponding to the various transitions, is considered in detail. It is shown that the presence of nuclear electric quadrupole moment introduces subsidiary minima into the spectrum; from the energy differences between these minima, one can derive the value of the constant ${e}^{2}\mathrm{qQ}$ ($e$ is the electronic charge, $Q$ is the nuclear electric quadrupole moment, and $q$ is a constant, depending on the charge distribution of the rest of the molecule, which must be independently evaluated in each case). The possibility of experimental application of these results is discussed. From heretofore unpublished data, we obtain a value for ${e}^{2}\mathrm{qQ}$ of ${\mathrm{Li}}^{7}$ in LiF of 1.0\ifmmode\pm\else\textpm\fi{}0.5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}21}$ erg. This may be compared with 0.3\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}21}$ erg for D in HD and ${\mathrm{D}}_{2}$.