Europium and CN⁻ Molecules

Abstract

Among the divalent rare-earth defects, the isolated Eu²⁺ ion has been studied most intensively in the past in numerous ionic crystals, including the alkali halides [1]. Owing to the high quantum efficiency of its blue emission, it has been considered as an active ion for laser operation and other applications based on its luminescence properties (e.g. X-ray storage, optical memory [2], and dosimeters [3, 4]). All of these applications use the blue Eu²⁺ emission for probing and would profit from a further increase of the quantum efficiency and a shift of the emission energy to longer wavelengths, into the spectral range (≈ 700 nm) in which simple Si detectors and CCD arrays are most sensitive. In this chapter, it will be shown that this can indeed be made possible by doping with CN^-.