Coulomb-excitation experiments are performed with postaccelerated beams of neutron-deficient Po196,198,200,202 isotopes at the REX-ISOLDE facility. A set of matrix elements, coupling the low-lying states in these isotopes, is extracted. In the two heaviest isotopes, Po200,202, the transitional and diagonal matrix elements of the 2+1 state are determined. In Po196,198 multistep Coulomb excitation is observed, populating the 4+1,0+2, and 2+2 states. The experimental results are compared to the results from the measurement of mean-square charge radii in polonium isotopes, confirming the onset of deformation from Po196 onwards. Three model descriptions are used to compare to the data. Calculations with the beyond-mean-field model, the interacting boson model, and the general Bohr Hamiltonian model show partial agreement with the experimental data. Finally, calculations with a phenomenological two-level mixing model hint at the mixing of a spherical structure with a weakly deformed rotational structure.We acknowledge the support of the ISOLDE Collaboration and technical teams and, especially, the support of RILIS and REX. This work was supported by FWO-Vlaanderen (Belgium), by GOA/2010/010 (BOF KU Leuven), by the Interuniversity Attraction Poles Programme initiated by the Belgian Science Policy Office (BriX network P7/12), by the European Commission within the Seventh Framework Programme through I3-ENSAR (Contract No. RII3-CT-2010-262010), by the German BMBF under Contract Nos. 05P12PKFNE, 06DA9036I 05P12RDCIA, and 05P12RDCIB, by the UK Science and Technology Facilities Council, by the Spanish MINECO under Project No. FIS2011-28738-C02-02, by Narodowe Centrum Nauki (Polish Center for Scientific Research) Grant No. UMO-2013/10/M/ST2/00427, by the Academy of Finland (Contract No. 131665), and by the European Commission through the Marie Curie Actions call PIEFGA-2008-219174 (J.P.)

The neutron-deficient nucleus 199 At has been studied through γ -ray and electron spectroscopy, using the recoil-decay tagging technique. Two experiments were conducted, using a gas-filled recoil separator with a focal-plane spectrometer alone and together with a germanium-detector array at the target position. The resulting level scheme for 199 At includes a new isomer with a half-life of 0.80(5) µs and a spin and parity of (29/2 + ). The 13/2 + isomer, which de-excites via an M2 transition to the 9/2 − ground state, was measured to have a half-life of 70(20) ns. Our earlier version of the level scheme for 197 At has been updated as well.

Using fusion-evaporation reactions, a gas-filled recoil separator, and recoil-electron and recoil-electron-α tagging techniques, a new isomeric 1 2 201 At is identified, and an earlier reported corresponding state [T 1/2 = 273( 9) ms] in 199 At is confirmed. The 1 2 + state is suggested to originate from an intruder π (s 1/2 ) −1 configuration. In addition, nuclear structure of states below and above this 1 2 + state are studied in both nuclei. The isomer decays through a cascade of an E3 transition followed by a mixed M1/E2 transition to the 9 2 − ground state, and it is interpreted to be fed from nearly spherical 3 2 + and 5 2 + states originating from π (d 3/2 ) −1 and π (d 5/2 ) −1 configurations, respectively.

Gamma rays from excited states feeding a proton-emitting isomeric-state in 151 Lu have been observed for the first time. Comparison with state-of-the-art nonadiabatic quasiparticle calculations indicates an oblately deformed, 3/2 + proton-emitting state with a quadrupole deformation of β 2 = −0.11. The calculations suggest an increase in quadrupole deformation, to β 2 = −0.18, with increasing spin which is understood in terms of the mixing of Nilsson states at the Fermi surface. It is also shown that the proton decay half-life is consistent with that from a 3/2 + state with a quadrupole deformation of β 2 = −0.12.

The nucleus 203 Fr has been studied through γ -ray and electron spectroscopy, using the recoil-decay tagging technique. A 13/2 + state, with a half-life of 0.37 (5)