Influence of Different Collective Coordinates on Spontaneous Fission Process in Fm Isotopes.pdf

INFLUENCE OF DIFFERENT COLLECTIVE COORDINATES ON SPONTANEOUS FISSION PROCESS IN Fm ISOTOPES1 6 A. STASZCZAK and Z. LOJEWSKI 9 9 Department of Theoretical Physics, M. Curie–Sklodowska University 1 pl. M. Curie–Sklodowskiej 1, 20–031 Lublin, Poland r a M Abstract 1 2 We study the role of different collective degrees of freedom in spon- taneous fission process of even–even Fm isotopes. To find a proper 1 v collective space we examine a reach collection of nuclear shape param- 2 eters {βλ }, with λ=2,3,4,5,6 and 8; as well as the paring degrees of 3 0 freedom i.e. proton ∆p and neutron ∆n pairing gaps. On the basis 3 of the multidimensional dynamic–programming method (MDPM) the 0 optimal collective space {β , β , β , ∆ , ∆ } for Fm isotopes was found. 2 4 6 p n 6 9 / h 1 Introduction t - l It is commonly known that experimental values of the spontaneous fission c u half–lives (Tsf ) of nine even–even Fm isotopes (N = 142, 144, ..., 158) form n : approximately two sides of an acute–angled triangle with a vertex in N = 152. v The rapid changes in Tsf on both sides of 252Fm are particularly dramatic for i X the heavier Fm isotopes, where Tsf descends by about ten orders of magnitude r when one passes from 254Fm to 258Fm. This strong nonlinear behaviour of a Tsf vs. neutron number N produces go