Grudzevich O.T.
Institute of Atomic Energy, Obninsk, Russia
The structure of gamma spectra observed in neutron capture reactions is described by modelling of discrete levels. The tendency of structure to decrease as neutron energy increases is reproduced in calculations. Modification of E1 strength functions according to observed maximum values at low transition energy is proposed and tested on gamma spectra. It is shown that E1 and M1 strengths have the same values at energy 2 MeV. The energy dependence of the E3-transition strength function is derived from experimental data.
1. TROUBETZKOY, E.S., Statistical theory of gamma-ray spectra following nuclear reactions, Physical Review, 122 1 (1961) 212.
2. GRUDZEVICH, O.T., ZELENETSKIJ, A.V., IGNATYUK, A.V., PASHCHENKO, A.B., Method of harmonized description of isomer yields in neutron reactions, Yadernaya Fizika, 57 B.8 (1994) 1428 [in Russian].
3. IGNATYUK, A.V., Statistical characteristics of excited atomic nuclei, Moscow, Ehnergoatomizdat (1983) [in Russian].
4. GRUDZEVICH, O.T., IGNATYUK, A.V., ZELENETSKY, A.V., “Consistent systematics of level densities”, Proc. Int. Conf. on Nuclear Data for Science and Technology, Mito, Japan (1988) 1221.
5. KADMENSKIJ, S.G., MARKUSHEV, V.P., FURMAN, V.I., Radiation widths of neutron resonances and giant dipole resonances, Yadernaya Fizika, 37 2 (1983) 277 [in Russian].
6. POPOV, Yu.P., “Decay of highly excited states by α-particle emission”, Physics and Applications (Proc. Europhysics Topical Conference, Smolenice, 1982) vol. 10, Bratislava (1982) 121.
7. DZHILAVYAN, L.Z., KAUTS, V.L., FURMAN, V.I., CHUPRIKOV, A.Yu., Some problems of isomeric states population, Yadernaya Fizika, 51 2 (1990) 336 [in Russian].
8. DIETRICH, S.S., BERMAN, B.L., Atlas of photoneutron cross-sections obtained with monoenergetic photons, Atomic Data and Nuclear Data Tables, 38 (1988) 199-388.
9. KOPECKY, J., UHL, M., Test of gamma-ray strength functions in nuclear reaction model calculations, Physical Review, C41 5 (1990) 1941.
10. TIELENS, T.A.A., KOPECKY, J., ABRAHAMS, K., ENDT, P.M., The reaction Na-23(n,γ)Na-24 studied with unpolarized and polarized thermal neutrons, Nuclear Physics, A403 1 (1983) 13.
11. MICHAELSEN, S., HARKER A., LIEB, K.P. et al., Complete spectroscopy of Y-90 via the Y-89(n,γ) and Y-89(d,p) reactions, Nuclear Physics, A552 (1993) 232.
12. ALENIUS, G., ARNELL, S.E., SCHALE C., WALLANDER, E., Thermal-neutron capture investigation of the N = 107 isotopes of Yb-177 and Hf-179, Nuclear Physics, A186 (1972) 209.
13. FUBINI, A., PROSPERI, D., TERRASI, F., VATA, I., The Lu-175 (n,γ) reaction and level structure of Lu-176, Nuovo Cimento, A8 (1972) 748.
14. KLAY, N., KAEPPELER, F., BEER, H., et al., Nuclear structure of Lu-176 and its astrophysical consequences, Physical Review, C44 6 (1991) 2801.
15. VOIGNIER, J., JOLY, S., GREINIER, G., Capture cross-sections and gamma-ray spectra from interaction of 0.5 to 3.0 neutron with nuclei in the mass range A = 63 to 209, Nucl. Sci. Eng., 93 (1986) 43.
16. ENSDF - a computer file of evaluated nuclear structure data maintained by National Nuclear Data Center, BNL (file as of Nov. 1989).
17. GARDNER, M.A., GARDNER, D.G., Evaluation of neutron-induced reaction cross-sections of the neutron-deficient isotopes of europium and gadolinium, Preprint of LLNL, UCRL-JC-110650, USA (1992).
18. CHADWICK, M.B., YOUNG, P.G., Calculations of the production cross-sections of high-spin isomeric states in hafnium, Nucl. Sci. Eng., 108 (1991) 117-125.
19. GRUDZEVICH, O.T., Systematics of parameters of the spin dependence of the level density, Yadernaya Fizika, 58 10 (1995) 1758 [in Russian].
20. ENDT, P.M., Strengths of gamma-ray transitions in A = 91-150, Atomic Data and Nuclear Data Tables, 26 (1981) 47-91.
21. IGASHIRA, M., KITAZAWA, H., SHIMIZU, M., et al., Systematics of the pygmy resonance in keV neutron capture γ-ray spectra of nuclei with N = 82-126, Nuclear Physics, A457 (1986) 301.
22. COLLINS, C.B., CARROLL, J.J., TAYLOR, K.N., et al., Common thresholds and the role of deformations in the photoexcitation of isomers, Physical Review, C46 3 (1992) 952.
23. BLATT, J., WEISSKOPF, V.F., Theoretical nuclear physics, Moscow, Inostr. Lit.(1954) [in Russian].
24. GRUDZEVICH, O.T., Isomeric ratios of neutron radiative capture, Yadernaya Fizika, 61 1 (1998) [in Russian].
25. BELANOVA, T.S., IGNATYUK, A.V., PASHCHENKO, A.B., PLYASKIN, V.I., Neutron radiative capture, Moscow, Ehnergoatomizdat (1986) [in Russian].
26. KARAMIAN, S.A., DE BOER, J., OGANESSIAN, Yu.Ts., et al., Observation of photonuclear reactions on isomeric targets: 178Hfm2(γ,n)177Hfm2, 180Tam(γ,2n)178Tam,g and 180Tam(γ,p)179Hfm2, Zeitschrift für Physik, A356 (1996) 23.
