Yrast isomers in95Ag,95Pd,and

Abstract

The yrast level schemes of three neutron deficient nuclei with mass AϷ95 have been studied with the reaction 58 Niϩ 40 Ca at 135 MeV, using the GASP ␥-ray array, the ISIS silicon ball, and the n-ring neutron detector. Excited levels, including a (23/2 ϩ ) spin-gap isomer, are reported for the first time in the heaviest NϭZϩ1 nucleus experimentally investigated, 95 Ag. In 95 Pd, the yrast line above the ground state has been observed and connected to states above the known isomeric level 21/2 ϩ , showing for the first time that this is indeed a spin-gap isomer. In 94 Pd, the 95.6-keV isomeric transition was confirmed, and its E2 character was firmly established. The experimental observations are compared with current shell-model calculations.

High-spin structure of95Pd

“…Many of the levels found in these experiments had no unambiguous spin and parity assignments. In our previous work [10], we reported on the low-energy part of the level scheme, experimentally confirming the theoretical predictions regarding the existence of a 21/2 + spin-gap isomer in 95 Pd, by showing that its excitation energy is just 3 keV below that of the 17/2 + yrast state. This was possible by linking this level to higher-lying levels whose decay could be followed down to the ground state.…”

“…The level scheme of 95 Pd, as determined in the present experiment, was mainly built by investigating the γ -γ coincidence relationships in a matrix obtained in coincidence with protons (1 or 2) and neutrons. This level scheme including also the previously reported levels [10] is shown in Fig. 1.…”

“…The 95 Pd nucleus is in this mass region of interest and has been previously investigated in experiments using fusionevaporation reactions [6][7][8][9][10]. Many of the levels found in these experiments had no unambiguous spin and parity assignments.…”

“…By finding the excitation energy of the 17/2 + level, the energies of the previously known levels decaying to this state were also correctly assigned. The observed structure at energies below 5 MeV was previously well described by shell-model calculations [10] performed using the model space as described in Ref. [4].…”

β-delayed proton emission in the100Sn region

“…The discrepancy between the two half-lives was explained by the presence of 95 Pd contamination in the earlier βp study. Long-lived 1/2 − and 23/2 − isomers, predicted for 95 Ag [1], were observed to decay predominantly by γ emission with short lifetime limits of <500 ms and <16 ms, respectively [39,40]. The β decay of 95 Ag is therefore likely dominated by the decay of the ground state.…”