α decay of the very neutron-deficient isotopes 197–199Fr
Kalaninova, Z. × Andreyev, A. N. Antalic, S. Heßberger, F. P. Ackermann, D. Andel, B. Drummond, M. C. Hofmann, S. Huyse, Mark # Kindler, B. Lane, J. F. W. Liberati, V. Lommel, B. Page, R. D. Rapisarda, Elisa # Sandhu, K. Saro, S. Thornthwaite, A. Van Duppen, Piet #
Published for the American Physical Society by the American Institute of Physics
Decay properties of the very neutron-deficient isotopes 197–199Fr were studied at the velocity filter Separator for
Heavy Ion reaction Products (SHIP) at GSI in Darmstadt. The isotopes were produced in the 2n–4n evaporation channels of the fusion-evaporation reaction 60Ni+141Pr → 201Fr*. Improved α-decay properties of 199Fr were determined and the possible existence of two α-decaying states in this nucleus is discussed. For the isotope 198Fr a broad α-decay energy distribution was detected in the range of (7470–7930) keV and two α-decaying states were observed with half-lives of 1.1(7) and 15(3) ms. The new isotope 197Fr was identified based on the observation of one α-decay chain yielding Eα= 7728(15) keV and T1/2 = 0.6+3.0
−0.3 ms. The systematics of reduced α-decay widths are presented for neutron-deficient francium, radon, and astatine isotopes.