Physics Division Seminars bring us speakers on a variety of physics related subjects. Usually these are held in the Building 6008 large Conference Room, at 3:00 pm on the chosen day, but times and locations may vary. For more information, contact our seminar chairman,
Tel (Office): (865) 574-6124 (FAX): (865) 574-1268
A new framework for comparing fusion probabilities in reactions forming heavy elements is presented which eliminates both theoretical and experimental uncertainties and gives new insight into systematic behavior. This is first applied to the formation of isotopes of thorium, where it is found that production yields follow a simple systematic behaviour. The data consistently show that fusion is inhibited (probably by quasi-fission) by about a factor of 10 for projectiles ranging from Ar to Sn, with little dependence on shell structure in the projectile and target nuclei. Application to formation of isotopes of Nobelium shows much more drastic change in fusion probability as a function of entrance-channel conditions and evidence of a rapid damping with excitation energy of shell effects in fusion dynamics.