CORE-NONPENETRATING RYDBERG STATES: SPECTROSCOPIC BLACK HOLES
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Date
1994
Journal Title
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Publisher
Ohio State University
Abstract
At first glance the exchange of energy and angular momentum between a particle as light as an electron and a system as heavy as a molecular cation seems improbable and inefficient. Molecular Rydberg spectra can reveal the nature and strength of the $e^{-}$/Ion coupling mechanisms. Our studies of the alkaline earth monohalides (CaF, CaCl, BaP), examples of uniquely simple $e^{-}/MX^{+}$ system consisting of two closed shell ions $(M^{2+}$ and $X^{-}$) where $MX^{+}$ has enormous and easily calculable multipole moments, have revealed the outline of a simple picture of the $e^{-}/MX^{+}$ interaction mechanisms. There are two types of Rydberg series, \textbf{core-non penetrating} (near-integer effective principal quantum number $n^{*}$,negligible {l}-mixing, rapid {l}-uncoupling, unusual sensitivity to isotopic substitution or vibrational excitation through dependence of the multipole moments on the $M^{2+}$ to center-of-mass distance) and {core-penetrating} (severe {l}-mixing among all of the penetrating-{l}-values as manifest in $s\sim p\sim d \sim f$ supercomplexes, slow and incomplete {l}-uncoupling, and $n^{+-}$ scaling of fine structure $parameters^{1}$). The structure and dynamics of non penetrating series are well described by a long-range multipole $model^{2,3}$. Each penetrating series may be viewed as built on an $n^{3/2}$ scaled replica of a valence $state^{1}$, where the valence state is well described by ligand field $theory^{4}$. The picture is completed by outside the core dipole and quadrupole interactions between penetrating and non penetrating $series^{5}$. Although by revealing the values of the ion-core multipole moments and polarizabilities, the non penetrating series should pay a central role in describing the $e^{-}$/ion interaction, these series have been surprisingly resistant to direct, systematic exploration.
Description
$^{1}$J.M. Berg, J.E. Murphy, N.A. Harris, and R.W. Field, Phys. Rev. A 48, 3012 (1993). $^{2}$Ch. Jungen and E. Miescher, Canad. J. Phys. 47, 1770 (1969). $^{3}$E.E. Eyler and F.M. Pipkin, Phys. Rev. A. 27, 2462 (1983). $^{4}$S.F. Rice, H. Martin, and R.W. Field, J. Chem. Phys. 82, 5023 (1985). $^{5}$Z.J. Jakubek and R.W. Field, Phys. Rev. Lett. (1994).
Author Institution: Department of Chemistry, M.I.T.
Author Institution: Department of Chemistry, M.I.T.