First observation of proton emission from 117 La F. Soramel*, A. Guglielmetttf, L. Stroe° )+ , L. Miiller 0 , R. Bonetti 1 ', F. Malerbat, G.L. Poll*, C. Boiano^ A. Andrighetto 0 , Z.C. Li 0 '*, F. Scarlassara 0 , C. Signorini 0 , A. Dal Bello 0 , R. Isocrate 0 , Z.H. Liu 0 '*, M. Ruan 0 '*, M.Ivascu + , P.Bednarczyk*, C. Broude < * Physics Department and INFN University of Udine, Udine, Italy t General Physics Insitute and INFN University of Milan, Milan, Italy 0 Physics Department and INFN University of Padua, Padua, Italy °INFN - Laboratori Nazionali di Legnaro, Legnaro, Italy +NIPNE, Bucharest, Romania * IFJ Krakow, Krakow, Poland * CIAE Beijing, People Republic of China < Weizmann Institute of Science, Rehovot, Israel Abstract. We report the first measurament, at the XTU Tandem + LINAC acceler- ator of the Laboratori Nazionali di Legnaro, of the decay of the very neutron deficient nucleus 117 La using a 310 MeV 58 Ni beam on a 64 Zn target; the 117 La nucleus was populated via the (p,4n) evaporation channel. The Recoil Mass Spectrometer (RMS) was used to select M/q = 117/30 recoils that were implanted in a (40x40) mm 2 Double Sided Silicon Strip Detector (DSSD) detector. The analysis has revealed that 117 La decays to 116 Ba via proton emission with E p — (783 ± 6)keV and T^ 2 —(20 ± 5) ms. Prom this result deformation parameters of ft2 —0.3 and ft4 = 0.1 have been deduced for the 117 La ground state which was assigned to J 71 " —3/2+. INTRODUCTION In recent years great progress has been achieved in mapping the p-dripline, also thanks to the identification of p-emitting nuclei [1]: The region between the two closed shells Z = 50 and Z = 82 has been mapped and for several elements more than one p-emitting isotope has been identified. For Z > 69 the p-emitting nuclei are spherical and their halflives and decay probabilities are well reproduced by various theoretical approaches; on the other hand, below Z = 68 p-emitters are strongly deformed in their ground state and the interpretation of the experimental results is not straightforward. Identification of many such cases, beside being important in obtaining information on nuclear binding energies of proton and daughter nuclei CP518, Proton-Emitting Nuclei: PROCON '99, edited by Jon C. Batchelder © 2000 American Institute of Physics l-56396-937-8/00/$17.00 68 Downloaded 13 Mar 2013 to 137.138.139.20. Redistribution subject to AIP license or copyright; see http://proceedings.aip.org/about/rights_permissions