Characteristics of the Transition-State Spectra for U234, U236, and Pu240 from (d,pf) and (t,pf) Angular-Correlation Experiments

Fission probabilities ofAm242,Cm243, and

“…The comparison of experimental fission probabilities with statistical model calculations [9] provided also indirect but compelling evidence that the first fission barrier is axially asymmetric for most of the actinide region, as predicted by theoretical calculations of the potential energy surface [10]. In addition, measurements of fission probabilities combined with fission-fragment angular distributions yield information on the properties of the transition states at the two saddle points through which the nucleus may pass on its way to fission [11][12][13][14].…”

“…4. The broad peaks at the highest excitation energies in the 4 He spectrum stem from transfer reactions on the 13 C present in the carbon backing and on 16 O, 19 F and 35,37 Cl impurities in the target. The background from reactions on the carbon support was measured separately with a carbon target with the same characteristics as the target backing.…”

Determining (n,f) cross sections for actinide nuclei indirectly: Examination of the surrogate ratio method

“…Angular correlations between the outgoing directreaction particle and fission fragments were studied in the 1960s for (d,pf), (t,pf), (t,df), and (α, α f) reactions [37][38][39][40][41][42][43]. For a given projectile-target combination, the distributions W(θ, φ) were found to depend on a variety of parameters: i) the energy E * to which the nucleus B * was excited in the direct reaction; ii) properties of the transition states populated in B * , such as the parity π of the relevant state, as well as the angular-momentum J and its projections K and M on the body-fixed and laboratoryfixed axes, respectively; iii) the angle ψ of the outgoing direct-reaction particle with respect to the beam direction.…”

Relative U235(n,γ) and (Allmond1, Bernstein2, Beausang3 et al. 2009Phys. Rev. C370200View full textAdd to dashboardCite

“…However, without 4π coverage, departures from the geometric efficiency can occur in the event of fission-fragment anisotropy. In order to investigate the effect of fission-fragment anisotropy on the fission-channel tagging efficiency, a systematic analysis was carried out and compared to past 235 U(d,pf) experiments [21][22][23]. The anisotropy is reduced by the relatively large target spin of J π = 7/2 − for 235 U and low angular-momentum transfer of < 3−4 for the (d,p) reaction.…”