title: Two-Proton Radioactivity of ^{67}Kr.
abstract: In an experiment with the BigRIPS separator at the RIKEN Nishina Center, we observed two-proton (2p) emission from ^{67}Kr. At the same time, no evidence for 2p emission of ^{59}Ge and ^{63}Se, two other potential candidates for this exotic radioactivity, could be observed. This observation is in line with Q value predictions which pointed to ^{67}Kr as being the best new candidate among the three for two-proton radioactivity. ^{67}Kr is only the fourth 2p ground-state emitter to be observed with a half-life of the order of a few milliseconds. The decay energy was determined to be 1690(17) keV, the 2p emission branching ratio is 37(14)%, and the half-life of ^{67}Kr is 7.4(30) ms.
authors: Centre d'Études Nucléaires de Bordeaux Gradignan, Université de Bordeaux-UMR 5797 CNRS/IN2P3, Chemin du Solarium, 33175 Gradignan, France.
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authors: Centre d'Études Nucléaires de Bordeaux Gradignan, Université de Bordeaux-UMR 5797 CNRS/IN2P3, Chemin du Solarium, 33175 Gradignan, France.
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authors: Centre d'Études Nucléaires de Bordeaux Gradignan, Université de Bordeaux-UMR 5797 CNRS/IN2P3, Chemin du Solarium, 33175 Gradignan, France.
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authors: Centre d'Études Nucléaires de Bordeaux Gradignan, Université de Bordeaux-UMR 5797 CNRS/IN2P3, Chemin du Solarium, 33175 Gradignan, France.
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authors: RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
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authors: RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.|Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
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authors: Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan.|Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka 567-0047, Japan.
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authors: Instituto de Física Corpuscular, CSIC-Universidad de Valencia, E-46071 Valencia, Spain.|Department of Physics, University of Surrey, Guildford GU2 7XH, United Kingdom.
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authors: Comisión Chilena de Energía Nuclear, Casilla 188-D, Amunátegui 95, Santiago Centro, Santiago, Chile.
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authors: Department of Physics and Astronomy, University of Tennessee, 401 Nielsen Physics Building, 1408 Circle Drive, Knoxville, Tennessee 37996-1200, USA.
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