16 Systematic Study of Po Compound Nuclei Using Evaporation Residue …
229
width with respect to the other decay channels changes which results in a higher value
for β to fit the experimental data. It is further interesting to note in this figure that the
β values for the above two cases tend to merge to a common value at higher excitation
energies which is a consequence of reduced shell effects at higher excitations.
The comparison of the above results with
48 Ti+
144,154 Sm system [10] clearly
indicates that the strength of nuclear dissipation required to fit the neutron multiplicity
data is very high as compared to results for
18 O+
192 Os. These calculations clearly
suggest the role of entrance channel dynamics for the systems considered here.
Lastly, we observe that the best fit β values at high excitation energies for
210 Po
are very close for both the cases. This indicates that shell effects on β, if any, are
small at high excitation energies.
16.4 Conclusion
SM calculations have been performed for
210 Po CN populated through
16 O +
192 Os
in the excitation energy range 52.43–83.51 MeV for which experimental data on ER,
fission cross-section, and neutron multiplicity is already available in the literature [9].
These calculations have been performed by using Bohr–Wheeler and Kramers’ formalism by including and excluding shell effects in the level density and the fission
barrier. The results of the ER and fission cross-section obtained from SM calculations
strongly indicate the need of using excitation energy-dependent scaling factor of the
finite-range rotating liquid drop model fission barrier in order to fit the experimental
data. The comparison of the pre-scission neutron multiplicities obtained from the
SM calculations with the experimental values clearly shows that the Bohr–Wheeler
fission width considerably underestimates the pre-scission neutron multiplicity at
all the energies. However, the calculations which take into consideration Kramers’
fission width are in well agreement with the experimental data. The comparison of
the SM results presented in this chapter with the results obtained for
48 Ti+
144,154 Sm
system clearly indicate the role of entrance channel dynamics for the systems [10]
considered in the present work.
References
1. K. Mahata, S. Kailas, Reexamination of fission in the A - 200 mass region with excitation
energy near 50 MeV. Phys. Rev. C 95, 054616 (2017)
2. C. Schmitt, K. Mazurek, P. Nadtochy, Description of isotopic fission-fragment distributions
within the Langevin approach. Phys. Rev. C 91, 041603(R) (2015)
3. K. Mahata, S. Kailas, S.S. Kapoor, Shell corrections at the saddle point for mass region 200.
Phys. Rev. C 74, 041301(R) (2006)
4. K. Mahata, S. Kailas, A. Shrivastava, A. Chatterjee, A. Navin, P. Singh, S. Santra, B. Tomar,
Fusion of 19 F with 188,192 Os. Nucl. Phys. A 720, 209 (2003)
229
width with respect to the other decay channels changes which results in a higher value
for β to fit the experimental data. It is further interesting to note in this figure that the
β values for the above two cases tend to merge to a common value at higher excitation
energies which is a consequence of reduced shell effects at higher excitations.
The comparison of the above results with
48 Ti+
144,154 Sm system [10] clearly
indicates that the strength of nuclear dissipation required to fit the neutron multiplicity
data is very high as compared to results for
18 O+
192 Os. These calculations clearly
suggest the role of entrance channel dynamics for the systems considered here.
Lastly, we observe that the best fit β values at high excitation energies for
210 Po
are very close for both the cases. This indicates that shell effects on β, if any, are
small at high excitation energies.
16.4 Conclusion
SM calculations have been performed for
210 Po CN populated through
16 O +
192 Os
in the excitation energy range 52.43–83.51 MeV for which experimental data on ER,
fission cross-section, and neutron multiplicity is already available in the literature [9].
These calculations have been performed by using Bohr–Wheeler and Kramers’ formalism by including and excluding shell effects in the level density and the fission
barrier. The results of the ER and fission cross-section obtained from SM calculations
strongly indicate the need of using excitation energy-dependent scaling factor of the
finite-range rotating liquid drop model fission barrier in order to fit the experimental
data. The comparison of the pre-scission neutron multiplicities obtained from the
SM calculations with the experimental values clearly shows that the Bohr–Wheeler
fission width considerably underestimates the pre-scission neutron multiplicity at
all the energies. However, the calculations which take into consideration Kramers’
fission width are in well agreement with the experimental data. The comparison of
the SM results presented in this chapter with the results obtained for
48 Ti+
144,154 Sm
system clearly indicate the role of entrance channel dynamics for the systems [10]
considered in the present work.
References
1. K. Mahata, S. Kailas, Reexamination of fission in the A - 200 mass region with excitation
energy near 50 MeV. Phys. Rev. C 95, 054616 (2017)
2. C. Schmitt, K. Mazurek, P. Nadtochy, Description of isotopic fission-fragment distributions
within the Langevin approach. Phys. Rev. C 91, 041603(R) (2015)
3. K. Mahata, S. Kailas, S.S. Kapoor, Shell corrections at the saddle point for mass region 200.
Phys. Rev. C 74, 041301(R) (2006)
4. K. Mahata, S. Kailas, A. Shrivastava, A. Chatterjee, A. Navin, P. Singh, S. Santra, B. Tomar,
Fusion of 19 F with 188,192 Os. Nucl. Phys. A 720, 209 (2003)