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The new proton radioactivities 165,166,167 Ir and 171 Au have been observed. The Ir isotopes were produced via the 92 Mo( 78 Kr,pxn) 165,166,167 Ir reactions at 357 and 384 MeV. 171 Au was produced via the 96 Ru( 78 Kr,p2n) 171 Au reaction at 389 MeV. The proton emitters were each identified by position, time, and energy correlations between the implantation of a residual nucleus into a double-sided silicon strip detector, the observation of a decay proton, and the subsequent observation of a decay alpha particle from the daughter nucleus ͑ 164,165,166 Os and 170 Pt, respectively͒. Both 166 Ir and 167 Ir have proton-emitting ground and isomeric states, which also decay by alpha emission. The proton-decay rates have been reproduced by calculations using the WKB barrier penetration approximation and a low-seniority shell-model calculation of the spectroscopic factors. The alpha decays of the four nuclei are followed by chains of alpha decays, allowing the determination of single-particle orbital orderings. Mass information has also been obtained from the alpha-decay chains because a connection to a known mass can be obtained for one of the nuclei. Ground-state mass excesses are reported for 151 Tm, 154 Yb, 155 Lu, 158 Hf, 159 Ta, 162 W, 163 Re, 166 Os, 167 Ir, and 170 Pt. The mass excess for 171m Au is also given. Proton separation energies are also deduced for the odd-Z alpha daughter nuclei of the Ir proton emitters.

The complete three-body correlation pictures are experimentally reconstructed for the two-proton decays of the 6 Be and 45 Fe ground states. We are able to see qualitative similarities and differences between these decays. They demonstrate very good agreement with the predictions of a theoretical three-body cluster model. Validity of the theoretical methods for treatment of the three-body Coulombic decays of this class is thus established by the broad range of lifetimes and nuclear masses spanned by these cases. Implementations for decay dynamics and nuclear structure of 2p emitters are discussed.

By studying the (109)Xe→(105)Te→(101)Sn superallowed α-decay chain, we observe low-lying states in (101)Sn, the one-neutron system outside doubly magic (100)Sn. We find that the spins of the ground state (J=7/2) and first excited state (J=5/2) in (101)Sn are reversed with respect to the traditional level ordering postulated for (103)Sn and the heavier tin isotopes. Through simple arguments and state-of-the-art shell-model calculations we explain this unexpected switch in terms of a transition from the single-particle regime to the collective mode in which orbital-dependent pairing correlations dominate.

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Ground and isomeric proton and alpha decay branches are reported for the new isotope 177 Tl, produced by bombarding a 102 Pd target with a 370 MeV beam of 78 Kr ions. The ground state is assigned as a s 1/2 configuration and the high spin isomer is assigned as a (h 11/2 ) Ϫ1 configuration. The ground-state proton decay of 171 Au has been identified for the first time, produced by bombarding a 96 Ru target with 78 Kr ions. The 171 Au ground state is also assigned as a s 1/2 configuration. Spectroscopic factors, masses, and proton separation energies are derived using these new proton decay measurements. New ground-state ␣ decays for 169 Ir and 173 Au are also reported. ͓S0556-2813͑99͒50206-9͔ PACS number͑s͒: 23.50.ϩz, 23.60.ϩe, 21.10.Pc, 27.70.ϩq Proton radioactivity measurements in the region of the drip-line from Zϭ69-79 ͓1͔ have revealed detailed information on the positions of single-particle levels, proton binding, and proton decay rates. In all cases protons have been identified as originating from approximately degenerate s 1/2 , d 3/2 , or h 11/2 orbitals. A proton decay spectroscopic factor S l j derived from a low seniority shell model calculation assuming degenerate single particle states reproduces the systematic variation in proton decay rates very well ͓1͔, as does a more sophisticated approach ͓2͔. It is of interest to extend these measurements to Tl nuclei since they reside immediately below the Zϭ82 shell closure. The most neutrondeficient Tl isotope identified to date is 179 Tl ͓3,4͔, which has ␣-decay branches from a low and a high spin state. Nearer to stability it has been shown that odd-A Tl isotopes are characterized as having a s 1/2 ground state with an isomeric h 9/2 intruder state configuration that involves the promotion of a proton from the s 1/2 orbital across the Z ϭ82 shell closure ͓5͔. It is known that these intruder states reach a minimum excitation energy of 281 keV for 189 Tl, which approximately corresponds to the neutron mid-shell. On either side of this minimum there is predicted to be a parabolic increase in excitation energy of the intruder due to the reduced interaction strength between the valence neutrons and the proton hole ͓6͔. This behavior is closely followed nearer to stability, but the information on neutrondeficient isotopes is somewhat limited, with 183 Tl being the lightest isotope for which the intruder state has been clearly identified ͑at an excitation energy of 625 keV ͓7͔͒. It is clearly of great interest to identify proton radioactivity from Tl isotopes both to obtain insight into the variation in proton decay rates in this region, and to study the low energy structure at the extreme limit of stability. The present paper describes a successful search for proton radioactivity from 177 Tl. A 4 pnA beam of 370 MeV 78 Kr ions from the Argonne ATLAS accelerator facility was used to bombard a 1 mg/cm 2 78% enriched 102 Pd target for a period of 65 hours in order to produce 177 Tl nuclei via the 1 p2n fusionevaporation channel. The Argonne Fragment Mass Analyz...

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