Program - Brookhaven National Laboratory

instances: 180m Ta (by bremsstrahlung [3] and Coulomb excitation [4]); 68m Cu (by Coulomb excitation [5]);
and 177m Lu and 178m2 Hf (by thermal neutrons [6, 7]). Recently, initial evidence has been reported on the
depletion of 108m Ag using bremsstrahlung [8]. While the very existence of isomers reflects specific aspects
of nuclear structure, i. e., spin and K trapping, the discovery of depletion mechanisms has provided new
insights into nuclear physics and new nuclear data. Examples include a partial synthesis of spectroscopic
and depletion studies for 180 Ta [9] and the discovery [10] of K hindrance in the rare α-decay branch of
178m2 Hf. This presentation will describe results from recent experiments, including spectroscopic and
depletion studies of 108m Ag, and the development of a depletion experiment for the 1200 year isomer of
166 Ho.
[1] H. Roberts, Hyperfine Int. 107, 91 (1997). [2] J. J. Carroll, et al., Hyperfine Int. 135, 3 (2001). [3]
D. Belic, et al., Phys. Rev. Lett. 83, 5242 (1999). [4] M. Schumann, et al., Phys. Rev. C 58, 1790
(1998). [5] G. Georgiev, et al., Intl. J. Modern Physics E 15, 1505 (2006). [6] O. Roig, et al., Phys.
Rev. C 83, 064617 (2011). [7] S. A. Karamian and J. J. Carroll, Phys. Rev. C 83, 024604 (2011).
[8] Induced depletion of 108mAg with 6 MeV bremsstrahlung, J. J. Carroll, in American Physical Society
April Meeting, Atlanta, GA, 2012. [9] P. M. Walker, et al., Phys. Rev C 64, 061302 (2001). [10] S. A.
Karamian, et al., Phys. Rev. C 75, 057301 (2007).
CD 3 2:20 PM
Beta-Decay Half-Lives and Delayed Neutron Emission Branchings of Very Neutron-Rich
Nuclei
I.N. Borzov
Nuclear Data Centre, Institute of Physics and Power Engineering, Obninsk, Russia, Bogolubov
Laboratory of Theoretical Physics, Joint Institute of Nuclear Research, Dubna, Russia
Nuclear masses, β-decay half-lives and beta-delayed branchings of very neutron-rich nuclei reflect an
imprint of nuclear structure evolution far from the stability valley. A substantial amount of new data on
the fission and fragmentation products are expected to come from the acting radioactive beam facilities
(ISOLDE-CERN, ALTO, RIKEN, NSCL) and FAIR, Spiral-2, HIE-CERN Projects. Precise masses and
beta-rates measurements of extremely neutron-rich nuclei are indispensable for the r-process modeling.
Accurate beta-decay data on fission products are of need for advanced reactor safety studies. To suffice
for numerous applications, the new evaluation of the beta-decay half-lives and delayed neutron emission
rates (Pn-values) [1] should acquire not only the new experimental data but also theoretical predictions for
nuclides beyond the reach of existing facilities. The fully microscopic models based on the first-principles
approach are of a special importance for decay data evaluation, as only they may ensure more reliable
extrapolation to extreme N/Z ratios [2]. The large-scale calculations of the half-lives and delayed neutronemission
rates of (near) spherical nuclides within the self-consistent Density Functional + Continuum
QRPA approach [3,4] will be presented. A special attention is paid to the delayed multi-neutron emission
rates P2n,3n near the closed shells. It is shown that the DF+CQRPA model provides better description
of the recent experimental beta-decay half-lives and delayed neutron emission rates [3-5] for the nuclei
near and beyond the neutron closed shells N=28, 50, 82, 126 than the standard global approaches [7,8].
Supported by the JIHIR, ORNL and partially by the IN2P3-RFBR under agreement 110291054.
1. D. Abriola, B. Singh, I. Dillmann., INDC(NDS)-0594, 2011. 2. http:// www.unedef.org 3. I.N. Borzov,
Phys.Rev. C67, 025802 (2003). 4. J. Winger et al . Phys.Rev. Lett. 102, 142502 (2009). 5. M. Madurga
et al. Phys. Rev. Lett. 2012, accepted. 6. I.N. Borzov, Phys.At. Nucl. 74, 1435 (2011). 7. B. Pfeiffer, et
al., Prog.Nucl. Energ. 41,39 (2002). 8. P. Moeller et al., Phys.Rev. C67, 055802 (2003).
47