title: Unexpected behavior of heavy-ion fusion cross sections at extreme sub-barrier energies.
abstract: The excitation function for fusion evaporation in the (60)Ni+ (89)Y system was measured over a range in cross section covering 6 orders of magnitude. The cross section exhibits an abrupt decrease at extreme sub-barrier energies. This behavior, which is also present in a few other systems found in the literature, cannot be reproduced with present models, including those based on a coupled-channels approach. Possible causes are discussed, including a dependence on the intrinsic structure of the participants.
authors.affiliation: Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: C L
authors.initials: CL
authors.lastname: Jiang
authors.forename: H
authors.initials: H
authors.lastname: Esbensen
authors.forename: K E
authors.initials: KE
authors.lastname: Rehm
authors.forename: B B
authors.initials: BB
authors.lastname: Back
authors.forename: R V F
authors.initials: RV
authors.lastname: Janssens
authors.forename: J A
authors.initials: JA
authors.lastname: Caggiano
authors.forename: P
authors.initials: P
authors.lastname: Collon
authors.forename: J
authors.initials: J
authors.lastname: Greene
authors.forename: A M
authors.initials: AM
authors.lastname: Heinz
authors.forename: D J
authors.initials: DJ
authors.lastname: Henderson
authors.forename: I
authors.initials: I
authors.lastname: Nishinaka
authors.forename: T O
authors.initials: TO
authors.lastname: Pennington
authors.forename: D
authors.initials: D
authors.lastname: Seweryniak