Posit Ron a Nnihila Ti on I N Pure a Nd Hydroge Nate D Palla Dium Deform Ed by Unia X Ia L Te Nsion

A ngular distri buti ons of the positron annihil ati on quanta were measured for pure and hydrogenated palladi um samples deformed by unia xi al tension up to di ̃erent deformation degrees. T he relative di ̃erence curves, and the values of the R parameter characteri zing the dimensions of defects trapping the positrons, w ere determined. I t w as found that for relative elongation s ranging from 1.9 to 3.5%, in both the pure and hydrogenated pallad iu m, the p ositrons are trapp ed in defects larger than vacancy clusters. T he values of the R parameter for pure palladi um samples elongated up to 0.39, 0.77, and 1.5% indicate a dominant role of smaller defects, like the vacancy clusters. PAC S numb ers: 78.70.Bj