First search for 2 epsilon and epsilon beta(+) decay of Er-162 and new limit on 2 beta(-) decay of Er-170 to the first excited level of Yb-170

摘要

The first search for double electron capture (2 epsilon) and electron capture with positron emission (epsilon beta(+)) of Er-162 to the ground state and to several excited levels of Dy-162 was realized with 326 g of highly purified erbium oxide. The sample was measured over 1934 h by the ultra-low background HP Ge gamma spectrometer GeCris (465 cm(3)) at the Gran Sasso underground laboratory. No effect was observed, the half-life limits were estimated at the level of lim T-1/2 similar to 10(15)-10(18) yr. A possible resonant 0 nu KL1 capture in( 162)Er to the 2(+) 1 782.7 keV excited state of Dy-162 is restricted as T-1/2 >= 5.0 x 10(17) yr at 90% C.L. A new improved half-life limit T-1/2 >= 4.1 x 10(17) yr was set on the 2 beta(-) decay of( 170)Er to the 2(+) 84.3 keV first excited state of Yb-170.