"Fission rate and time of highly excited nuclei in multi-dimensional stochastic calculations"
Yuri Anischenko, Omsk State University, Russia
(id #106)
Seminar: YesPoster: No
Invited talk: No
The impact of dimensionality of the dynamical model in use on the fission rate and time is studied within the stochastic approach to fission dynamics. The evolution of the system was described by multidimensional Langevin equation for the elongation and orientation degrees of freedom[1]. One-, two- and three-dimensional cases were considered on the basis of the
{c, h, α}-parametrization of the nuclear surface shape.
It was shown in [2] that it’s very important to take into account orientation(K state) degree of freedom to correctly calculate fission lifetimes. K state, which is the angular moment onto the elongation axis, was incorporated into our Langevin calculations and treated as the fourth
overdamped coordinate. It was demonstrated that the inclusion of K state leads to the decrease in the stationary fission rate and increase in the mean fission time. Such observations based on the fact that K state can give a significant rise to the fission barrier height. The increase in the
mean fission time is about 1.5 − 2 times for the reactions with compaund nuclei with excitation energy 200 MeV.
The influence of the dissipation mechanism on the transient time is studied for multi-dimensional systems. It was shown that the ratios of the stationary fission rates obtained in the calculations with the different dimensionalities remain almost the same for different dissipation mechanisms. Thus we conclude that the fission rate is mostly determined by the structure of the potential energy surface of the system[3].
Calculations were performed for the large number of compound nuclei with Z^2/A parameter in the range 20 < Z^2/A < 40. A considerable increase of the stationary fission rate in the transition from one-dimensional to three-dimensional case was revealed. This increase is particularly substantial for the light fissile nuclei near the Businaro–Gallone point. Comparison of the dynamically calculated stationary fission rate and Kramers rate was also made. Fission time was calculated for considered reactions, where particle evaporation was taken into account. The tremendous influence of the dimensionality of the dynamical model on the fission rate and time led us to note about the importance of the inclusion of the many coordinates into the statistical calculations of fission widths.
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[1] G. D. Adeev, A. V. Karpov, P. N. Nadtochy, D. V. Vanin, Phys. Part. Nucl. 36, 732 (2005).
[2] J. P. Lestone and S. G. McCalla, Phys. Rev. C 79, 044611 (2009).
[3] Yu. A. Anischenko, A. E. Gegechkori, P. N. Nadtochy, G. D. Adeev, Phys. At. Nucl., 72, 2056(2009).
{c, h, α}-parametrization of the nuclear surface shape.
It was shown in [2] that it’s very important to take into account orientation(K state) degree of freedom to correctly calculate fission lifetimes. K state, which is the angular moment onto the elongation axis, was incorporated into our Langevin calculations and treated as the fourth
overdamped coordinate. It was demonstrated that the inclusion of K state leads to the decrease in the stationary fission rate and increase in the mean fission time. Such observations based on the fact that K state can give a significant rise to the fission barrier height. The increase in the
mean fission time is about 1.5 − 2 times for the reactions with compaund nuclei with excitation energy 200 MeV.
The influence of the dissipation mechanism on the transient time is studied for multi-dimensional systems. It was shown that the ratios of the stationary fission rates obtained in the calculations with the different dimensionalities remain almost the same for different dissipation mechanisms. Thus we conclude that the fission rate is mostly determined by the structure of the potential energy surface of the system[3].
Calculations were performed for the large number of compound nuclei with Z^2/A parameter in the range 20 < Z^2/A < 40. A considerable increase of the stationary fission rate in the transition from one-dimensional to three-dimensional case was revealed. This increase is particularly substantial for the light fissile nuclei near the Businaro–Gallone point. Comparison of the dynamically calculated stationary fission rate and Kramers rate was also made. Fission time was calculated for considered reactions, where particle evaporation was taken into account. The tremendous influence of the dimensionality of the dynamical model on the fission rate and time led us to note about the importance of the inclusion of the many coordinates into the statistical calculations of fission widths.
-------
[1] G. D. Adeev, A. V. Karpov, P. N. Nadtochy, D. V. Vanin, Phys. Part. Nucl. 36, 732 (2005).
[2] J. P. Lestone and S. G. McCalla, Phys. Rev. C 79, 044611 (2009).
[3] Yu. A. Anischenko, A. E. Gegechkori, P. N. Nadtochy, G. D. Adeev, Phys. At. Nucl., 72, 2056(2009).
