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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