Discovery and Cross-Section Measurement of Neutron-Rich Isotopes in the Element Range from Neodymium to Platinum at the FRS

Abstract

With a new detector setup and the high-resolution performance of the fragment separator FRS at GSI we discovered 57 new isotopes in the atomic number range of 60$\le Z\le 78$: \nuc{159-161}{Nb}, \nuc{160-163}{Pm}, \nuc{163-166}Sm, \nuc{167-168}{Eu}, \nuc{167-171}{Gd}, \nuc{169-171}{Tb}, \nuc{171-174}{Dy}, \nuc{173-176}{Ho}, \nuc{176-178}{Er}, \nuc{178-181}{Tm}, \nuc{183-185}{Yb}, \nuc{187-188}{Lu}, \nuc{191}{Hf}, \nuc{193-194}{Ta}, \nuc{196-197}{W}, \nuc{199-200}{Re}, \nuc{201-203}{Os}, \nuc{204-205}{Ir} and \nuc{206-209}{Pt}. The new isotopes have been unambiguously identified in reactions with a ${}^{238}$U beam impinging on a Be target at 1 GeV/u. The isotopic production cross-section for the new isotopes have been measured and compared with predictions of different model calculations. In general, the ABRABLA and COFRA models agree better than a factor of two with the new data, whereas the semiempirical EPAX model deviates much more. Projectile fragmentation is the dominant reaction creating the new isotopes, whereas fission contributes significantly only up to about the element holmium.

arXiv comment9 pages, 4 figures

References in corpus (6)

• The End of Nucleosynthesis: Production of Lead and Thorium in the Early Galaxy
• Fission-Residues Produced in the Spallation Reaction 238U+p at 1 A GeV
• Improved Empirical Parametrization of Fragmentation Cross Sections
• Measurement of nuclide cross-sections of spallation residues in 1 A GeV 238U + proton collisions
• Production of new neutron-rich isotopes of heavy elements in fragmentation reactions of ${}^{238}$U projectiles at 1 A GeV
• Light Nuclides Produced in the Proton-Induced Spallation of 238U at 1 GeV

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