Switching ON / OFF “after-effects” with electron / gamma time differential correlations

by Correia, J.G. (Instituto Tecnológico e Nuclear, Portugal & ISOLDE CERN)

Thursday 1 Dec 2005, 14:00 → 15:00 Europe/Zurich

01-01-025 (CERN)

Often nuclear beta/ EC decay and conversion electron processes are accompanied by Auger electron emission leading to daughter atoms on highly ionized states. When the radioactive nuclei are embedded to matter, most of the atomic shells recombine very fast within 10^-15s. But, for one or two missing electrons, when the potentials approach the equilibrium value of the host matrix, depending on the material’s conductivity, the recombination can take longer times from nano-s to micro-s. Such phenomena, which have never been easy to characterize, become then observable on integral & time differential angular correlation experiments and are designated by “after-effects”.

We present a clean set of time differential perturbed angular correlation (TDPAC) experiments, comparing gamma-gamma with conversion electron-gamma experiments that measure the transient electric field gradients due to real after-effects on intrinsic n and Mg doped GaN samples, as well as on several insulators LiNbO₃, LiTaO₃, Al₂O₃ (sapphire) and SrTiO₃. In the present set of experiments, true After-effects are only observable with electron-gamma TDPAC, since they are triggered by the emission of the conversion electron.  The recombination of the highly ionized states will be fast or slow depending on the material and on the probe element relationship with the host. Ideas for studying materials problems, by the comparative use of the electron-gamma and gamma-gamma correlation techniques are drafted, particularly at ISOLDE where several probe elements are available.

Organiser(s): Guilherme Correia

Note: guilherme.correia@cern.ch