Radiation Research

Optical Absorption by a Pair of Ions

David L. Dexter

Published Sep 1, 1963• 3 citations

Abstract

tion of a single photon by a pair of rare-earth ions in a crystal, acting in cooperation. Neither ion by itself could possibly absorb the photon, since no single-ion state exists at the photon energies involved. Absorption of light occurs discretely at sums of energy-level separations in the two ions and is detected experimentally by the excitation spectrum of one of the emission lines. This is an extremely important new effect which will doubtless have important practical applications in the future as well as obvious scientific implications. It should be emphasized that this is not, in any significant degree, excitation of a molecular state. The basic reason this phenomenon is so unusual is related to the fact that the interaction of radiation with matter consists of a sum of one-electron operators, A Vi, where A is the vector potential. From this point of view, only one electron at a time could possibly be excited, hence only one ion. In this paper a procedure for computing the probability of this effect is outlined, and some of the implications of the associated phenomena are discussed. These views can be found expressed in greater detail in ref. 2.

DOI: 10.2307/3571338

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