Study of gamma decay of highly-excited states in medium-weight and heavy nuclei

Advisor: Milan Krtička (IPNP MFF CUNI)

Funding: Fully funded

Contact: krticka@ipnp.mff.cuni.cz

With presently available experimental techniques the complete spectroscopic data in medium- and heavy-mass nuclei can be obtained only for levels at lowest excitation energies below, at most up to about 2 MeV in even-even nuclei away from closed shells. These limitations originate mainly from the nuclear level density (NLD) rapidly increasing with excitation energy. Properties of medium-weight and heavy atomic nuclei at higher excitation energies are then described using the statistical model in terms of the NLD and a set of photon strength functions (PSFs) for different transition types. These quantities are necessary for calculations of cross sections in all reactions involving photons and are important especially in nuclear astrophysics [1, 2] and in the development of advanced nuclear reactors [3].

Important information on PSFs and NLD can be obtained from an analysis of coincident -ray spectra measured either in the decay of isolated neutron resonances, measured at the DANCE experiment at Los Alamos National Laboratory [4,5] or in the thermal neutron capture measured at the reactor at Řež near Prague [6].

The candidate will process data from at least one of these coincidence experiments. Experimental data will be tested against simulations of gamma decay within the statistical model of nucleus. A comparison of simulated and experimental spectra allows to make significant restrictions on acceptable NLD and PSFs models and on the validity of the statistical model of nucleus itself.

References

[1] G. J. Mathews and R. A. Ward, Rep. Prog. Phys. 48, 1371 (1985).
[2] C. Sneden, J. J. Cowan, and R. Gallino, Annu. Rev. Astron. Astrophys. 46, 241 (2008).
[3] Report of the Nuclear Physics and Related Computational Science R&D for Advanced Fuel Cycles Workshop, August 10-12, 2006, Bethesda, Maryland (2006)
[4] N. Simbirtseva et al., Phys. Rev. C 101, 024302 (2020)
[5] S. Valenta et al., Phys. Rev. C 96, 054315 (2017)
[6] S. Valenta et al., Phys. Rev. C 92, 064321 (2015)