Evaporation of 3 to 8 Neutrons in Reactions betweenC12and Various Uranium Nuclides

How well do we understand the synthesis of heavy elements by heavy-ion induced fusion?

“…2. Very good agreement between the experiment [37] and the calculation is achieved not only for the position of the maxima but also for absolute cross section values. The largest discrepancies as observed for the 7n and 8n evaporation channel are still less than a factor of three.…”

Study of fusion reactions forming Cf nuclei

“…The CN forms as a result of the equilibration of all the degrees of freedom in the two-center system. The measured ER cross sections of 12 C+ 235 U are on the order of µb's [20][21][22][23], which is also consistent with the conclusion that CN formation is dominant in this fusion reaction. A characteristic time for the fission events from this process is, however, not possible to determine.…”

“…It is interesting to note that the xn ER excitation functions of such asymmetric reactions (for example, 12 C+ 233-236,238 U [20][21][22][23]) yield maxima for the evaporation of 4-6 neutrons, which corresponds to roughly the same excitation energy region (from 35 to 55 MeV) in which flat-top distributions are observed in this work. In a late chance fission process, de-excitation of the CN occurs through different stages at each "newly" formed CN, with the reduced atomic mass number and reduced excitation energy enhancing survival against fission.…”

“…An assumption about the presence of late chance CNfissions can be easily made based on observed ERs in neutron evaporation channels [20][21][22][23]. It is interesting to note that the xn ER excitation functions of such asymmetric reactions (for example, 12 C+ 233-236,238 U [20][21][22][23]) yield maxima for the evaporation of 4-6 neutrons, which corresponds to roughly the same excitation energy region (from 35 to 55 MeV) in which flat-top distributions are observed in this work.…”

Odd-Z Transactinide Compound Nucleus Reactions Including the Discovery of 260Bh

“…The classic treatment regarding the synthesis of compound nuclei is from the work of Sikkeland et al [26], drawn from earlier work by Jackson [27]. This model treats CN formation as the product of two parameters: 1) The capture cross section of the projectile and target nuclei (also referred to as "sticking"), and 2) the probability of this excited CN to survive fission by emitting neutrons (or protons, or alpha particles; also referred to as "surviving").…”