Positron lifetime measurements in rochelle salt in presence of external electric field

Abstract

The positron lifetime measurements on Rochelle salt as a function of the intensity of the electric field were provided. Four lifetime components were observed, the shortest lifetime component, corresponding to para-positronium formation is constant. The positron trapping rate around the negative ions was found to be ki = 8.5 × 108s−1 in the whole investigated region. The trapping rate on the domain boundaries kd depends on the electric field applied and has maximum values when the domain polarization turns to the opposite direction. It was established existing of free volumes in the Rochelle salt crystal. The size of free volumes was independent on the electric field applied, except for the region where the domain polarization inversed. The free volume radius was calculated to be R0 = 1.72 A at the saturation values of the electric field. Our investigations show the presence of or the-positronium state in the crystal. The effective mass for the positronium atom calculated in the terms of the exciton theoretical model is 6.4 × 102m. All the measurements of positron lifetimes were done at RT.