Emission Sidebands of Eu2+-Doped Alkali Halides

Abstract
Emission spectra of Eu 2+ -doped KCI, KBr and NaCl arising from the transition 5d(4f) 6 →(4f) 7 have been measured at LHeT. Besides the previously known structure due to resonance modes, another vibronic structure has been found in KCl and NaCl. The structure has been analysed by the projected Green's function method, and attributed to van Hove singularities of the state density of the band mode phonons which couple to the electronic transition through the displacement of the equilibrium positions of the nearest or the next nearest neighbor unperturbed ions.