High-spin states and neutron-hole influence inAt209

Abstract

The properties of high-spin states in ' At have been studied with the ' Pb( Li, 3ny)' At reaction. In-beam measurements with Ge(Li) detectors of y-ray excitation functions, y-y cc incidences, y-ray angular distributions, and pulsed beam-y timing were made to establish decay schemes, level energies, spin-parity assignments, isomeric lifetimes, and magnetic moments. High-spin states involving three valence protons in the 1h9/2 2f7, 2 or 1i)3/ orbitals were identified. The electromagnetic properties observed in ' 'At were compared with those in the closed-neutron core nucleus "'At to examine the influence of the two neutron holes on the proton structure; microscopic calculations of this influence were carried out in perturbation theory.NUCLEAR REACTIONS 6Pb(6Li, any), El, =29-34 KIeV; measured y-excitations, y-y coincidences, y-W(0), pulsed beam-y timing, perturbed angular distributions; deduced level scheme, y multipolarities, J~, T&i&, B(E2), g factor; perturbation calculations.

Low- and medium-spin states in theN=124 isotones208Po and209At

“…The half-lives reported previously in high-spin works [21,26] have been confirmed and more accurate values have been obtained. The greatest discrepancy is found for the 577.6keV 29/2 +-23/2-transition in Z~ where the previously reported [27] value of 680 +75 ns has been redetermined to be 860 4-20ns, cf. also [13,26].…”

“…Some background-subtracted spectra are shown in Fig. 3, exemplifying the data for 2~ In addition to the yrast cascades reported earlier [21,26,27] a large number of non-yrast levels are observed in both nuclides. The older work on 2~176 decay [22] is largely revised, cf.…”

Detailed spectroscopy of Bi195

“…In the odd-A At isotopes, 29/2 + isomeric states have been observed [11][12][13][14][15]. They are assigned to the π (i 13/2 h 2 9/2 ) configuration.…”

“…A peak at the same energy also appears in the planar spectrum tagged by the prompt γ -ray transitions feeding the isomer, detected in JUROGAM II. We therefore attribute the 49 keV transition to the decay A conversion electron intensity analysis using the information obtained from the delayed γ -ray gated PIN spectra (γ -electron coincidences) resulted in a conversion electron intensity ratio K/(L + M + · · · ) = 1.37 (12) for the 307 keV transition, matching the theoretical value 1.26(4) for an E2 transition [41]. An E2 character assignment for this transition is also supported by the DCO ratio, which is 1.28(13), hence indicating a stretched quadrupole transition.…”

“…The structure of the isomer is associated with the coupling of an h 9/2 proton to the 12 + isomeric state in the 192 Pb core. In several odd-A At isotopes, isomeric states with a spin and parity of 29/2 + have been identified [11][12][13][14][15] and associated with the coupling of the h 9/2 proton to the π (h 9/2 i 13/2 ) configuration. Moreover, the search for highly excited superdeformed (SD) bands to better understand the nuclear properties under extreme deformation has turned out to be very successful in this region of the nuclear chart [8,[16][17][18][19][20].…”