Conclusions Perfluoro-2,4-dimethyl-2-fluorocarbonyl-1,3-dioxolane reacts with sodium carbonate to give perfluoro-2-methylene-2-methyl-1,3-dioxolane. Under the reaction conditions, the latter dimerizes to perfluoro-2-(2,4-dimethyl-1,3-dioxolan-2-ylmethylene)-4-methyl-1,3-dioxolane, and on treatment with CsF is converted into perfluoromethyl-(1,3-dioxolany-2-yl)ketone.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 938–942, April, 1989. 相似文献
A dynamical approach is proposed for calculating the angular distributions of fission fragments. The relaxation time for the degree of freedom associated with the projection of the total angular momentum of the nuclear system onto the symmetry axis and the coefficient of damping of the fission mode are the basic parameters of this approach. Experimental data on the anisotropy of the angular distributions of fission fragments and on the multiplicities of prescission neutrons are analyzed within the proposed model for 16O+208Pb (Elab=110–148 MeV), 16O+232Th (120–160 MeV), 16O+248Cm (110–148 MeV), and 16O+238U (96–148 MeV). The relaxation time and the damping coefficient are estimated at τK=(5–6)×10?21 s and β=4×1021 s?1, respectively. 相似文献
A dynamical model of fission fragment angular distributions is developed. The experimental data on the angular anisotropy of fission fragments is analyzed for the 16O + 208Pb, 232Th, 238U, and 248Cm reactions at energies of the incident 16O ions ranging from 90 to 160 MeV. This analysis allows us to extract the relaxation time for the tilting mode. It was also demonstrated that the angular distributions are sensitive to the deformation dependence of the nuclear friction.
A large set of experimental observables for the 232Th(α, xnf)reaction was analyzed theoretically within the dynamic-statistical approach, making it possible to interconsistently consider
the manifestation of nuclear viscosity, the double-humped structure of the fission barrier, and the phenomenon of shell effect
damping with temperature. Analyses were performed for the energy dependence of the finite lifetime effect in the investigated
reaction, obtained using the crystal blocking technique; the fission probability isotopes produced in this reaction during
the development of a neutron emission cascade; and the anisotropy of angular distributions of fission fragments. It is shown
that this analysis allows us to obtain information regarding nuclear viscosity and its energy dependence at relatively low
excitation energies (<30 MeV). 相似文献
The unified energy dependence of the induced fission times obtained by the crystal blocking technique for heavy nuclei with Z=91–94 in the range of initial excitation energy from 5 to 250 MeV was analyzed. It was demonstrated that, for excitation energies of the investigated heavy fissionable nuclei up to 60–70 MeV, the fission times can be described in the framework of the statistical theory of nuclear reactions taking into account the double-humped structure of the fission barrier and the lifetimes of both classes of excited nuclear states realized in the first and second potential wells. However, for excitation energies above 70 MeV, there is a need to consider the dynamical effects in the fission channel. 相似文献
A model of induced nuclear fission was developed with consideration of thermodynamically fluctuating orientation degree of
freedom (tilting) of deformed nuclei. This model was applied to analysis of the experimental angular anisotropy of fission
fragments in the 16O + 232Th, 238U, 248Cm, 208Pb, 209Bi; 12C + 236U; 19F + 208Pb; and 11B + 237Np reactions. Information on the equilibrating time of the tilting mode was obtained.
The text was submitted by the authors in English. 相似文献
Within a dynamical approach, the average spins of fission fragments originating from the 12C + 235,236U and 13C + 235U complete fusion reactions at c.m. energies in the range of Ec.m. = (55–75) MeV are analyzed as a function of energy. Particular attention is given to the process of formation of initial distributions for the components of the total angular momentum of compound nuclei. It is shown that substantial distinctions in the behavior of average spins of fission fragments for different fusion reaction channels are expected to be observed in the range of subbarrier energies.
A combined dynamical and statistical approach to describing induced fission of heavy nuclei is proposed. This approach takes
into account the nuclear-dissipation phenomenon and the double-humped structure of the fission barrier. A method that is intended
for calculating the angular distribution of fission fragments and which is applicable over a broad range of excitation energies
is discussed. The potential of the approach is demonstrated by addressing the problems of self-consistently describing experimental
data on fission probabilities for plutonium and americium isotopes, the yields of shape isomers in the α+238U reaction at alpha-particle energies in the range Eα = 20–32 MeV and the d+242,240Pu reactions at deuteron energies in the range Ed = 20–30 MeV, fission times in the α + 238U reaction at alpha-particle energies in the range Eα = 20–32 MeV, and angular distributions of fission fragments in the α + 238U, 237Np reactions at alpha-particle energies in the range Eα = 20–100 MeV. 相似文献