Abstract
Resonant secondary radiation (zero-phonon lines) flourescence spectra of isotopic 3D aggregates of traps (NH 8) in a host crystal (ND 8), as well as transfer-induced fluorescence at trap concentrations between 0.01 and 10% and at temperatures between 1.6 and 10 K, are presented. Laser-excited (0–1) resonant secondary (zero-phonon) emission is used to resolve close-lying electronic resonances, corresponding to monomers, aggregates and to their host and trap satellite lines, in a quasi-continuum of 3D trap states. Such states are also calculated by numerically diagonalizing a mixed-crystal 3D hamiltonian. Measured and calculated delocalization indices are given for all trap species. In addition, low-temperature spectral diffusion of photoselected trap species is measured by plotting the attenuation of the zero-phonon lines. We give a simple discussion on the modulation of the resonant secondary radiation spectra by concentration, excitation wavelength and temperature. We show that low-temperature exciton diffusion, assited by acoustical phonon creation, occurs above a very low concentration threshold ( C > 0.05% for monomers at T = 1.6 K). Thermally activated transfer of the photoselected excitons is also plotted for temperatures up to 10 K above which the zero-phonon lines are quenched.
Published Version
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