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In this work we present the results from two experiments dedicated to search for quadrupolecollective isovector valence-shell excitation, the states with so-called mixed proton-neutron symmetry (MSS), in nuclei around the doubly magic nucleus 208Pb. 212Po was studied in an α-transfer reaction. 204Hg was studied in an inverse kinematics Coulomb excitation reaction on a carbon target. Both experiments provide indications for existence of one-phonon MSSs. Those are the first experimentally identified MSSs in the mass A ≈ 208 region.

A new method of extracting the γ -ray intensities necessary to perform lifetime measurements using the differential decay curve method (DDCM) is presented in this work, the unresolved Doppler-shifted components method (UDCM). The UDCM allows for a DDCM analysis to be performed using a γ -ray transition for which the fully Doppler-shifted and degraded components are unresolvable in energy and so are detected as a single peak. This technique was used to measure the known lifetime of the yrast 2 1 + state in 50 Mn with a depopulating transition that does not have resolvable fully Doppler-shifted and degraded components. The lifetime measured through applying the UDCM was consistent with the standard DDCM measurement of the 2 1 + state. Use of the UDCM allows for DDCM lifetime measurements to be made using transitions of smaller γ -ray energies, smaller recoil velocities and, in some cases, with a smaller uncertainty. In contrast to a standard DDCM analysis, a UDCM analysis is also independent of the widths of the fully Doppler-shifted and degraded components and as a result they do not need to be determined. [ABSTRACT FROM AUTHOR]

Lifetimes of the T=1 isobaric analog Iπ=2+ states in 50Mn and 50Cr were measured simultaneously by employing the recoil distance Doppler-shift (RDDS) technique. The states were populated in a fusion-evaporation reaction with a 12C beam on a 40Ca target. An analysis of the data and the calculations from the present work, together with the available B(E2:2+→0+) data of the isobaric analog states in 50Fe and 50Cr, were used to study isospin symmetry in the three A=50 isobaric nuclei. Shell-model calculations reproduce the magnitudes as well as the increasing trend of the B(E2) data with increasing Z. To draw a firm conclusion on the level of isospin mixing in the triplet, a new precision measurement of the 2+→0+ transition rate in 50Fe will be required. [ABSTRACT FROM AUTHOR]