Hartree-Fock theory of nuclear deformations and high spin states

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362 C R Praharaj 7 6 0 EVEN BRANCH A ODD BRANCH 5 >
H F theory of nuclear deformations 363 > CII ::E 30 >- 0\ ~ 20 c CII c 0 -:u ~ 10 u )( W 152 66DYB6 0 0 10 20 30 1.0 '""" . . Low deformation ...,..." band ~ $ Oblate states 50 60 Spin (h) Fi\:ure 9. 1987). low deformation and superdeformcd bands in I~lDy (Twin et a/1986; Aberg et al 3.5 Superdeformed band at high spins In the study of very high spin states in 152Dy nineteen £2 transitions with strength of about 2500 Weisskopf units (WU) have been found (Twin et at 1986) signifying a supcrdcformed band at high spins. The transition energies range from 602 to 1449keV with a constant energy separation of 14keV with the spins extending from 22ft to 60ft. In comparison, the £2 transition strengths for low spin rotational bands in this mass region are about 200 WU. The superdeformed band is several MeV above the yrast line near spin 22ft and crosses the yrast band near 60ft(figure 9).The low spin yrast states of 152Dyare weakly prolate deformed and become oblate with rather irregular spacings around 26ft. Microscopic theoretical models of the superdeformed band have been attempted by the Lund group (Ragnarsson and Aberg 1986;Aberg et at 1987)and involve nucleonic orbits of very largej. For 152Dy the superdeformed band has components n(iI3/2)4 VV1512)2coupled to nucleons in lower spin orbitals. Superdeformed band has also been seen in 149Gd (Haas et aI1988). Possible structures for the superdeformed bands have been assigned (Bengtsson et al 1988).There is evidence for the onset of superdeformation in 154Dy (Ma et al 1988)for spins above 46ft. . 4. Conclusion Hartree-Fock calculations in different mass regions using a variety of interactions have been performed over the past two decades and have contributed much to our understanding of the structure, shape and various spectroscopic properties of nuclei. Hartree-Fock and diagonalization after angular momentum projection methods have also been applied to the study of high spin states and band-crossing in nuclei. States of very high spins and large deformations are now being seen in many regions of the periodic table and provide stimulus for the microscopic study of the structure of such unusual configurations.
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Hartree-Fock theory of nuclear deformations and high spin states

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