Chiral Structures in doubly odd nucleus 102Ag

Proceedings of the DAE Symp. on Nucl. Phys. 59 (2014)
Chiral Structures in doubly odd nucleus
V. Singh1 , S. Sihotra1 ,∗ G.H. Bhat2 , S. Kumar1 , K. Singh1 , N. Singh1 , J.
Goswamy1 , J. Sethi3 , S. Saha3 , R. Palit3 , J.A. Sheikh2 , and D. Mehta1
Department of Physics, Panjab University, Chandigarh-160014
Department of Physics, University of Kashmir, Srinagar-190 006 and
Department of Nuclear and Atomic Physics, TIFR, Mumbai-400005
The level strutures of nuclei approaching
the neutron and proton major shell closures
at N=Z=50 are complex due the interplay between the single-particle and collective degrees
of freedom. Various new deformation generating mechanisms have been identified in theoretical interpretation of the observed level
structures. Investigations have revealed diversity in level structures resulting from coupling of the g9/2 , d5/2 , g7/2 , and h11/2 valence nucleons and the core-excited configurations. The relevant intringuing triaxiality
based phenomena such as magnetic rotation
[1] and degenrate twin bands have been reported in this mass region [2]. The twin
degenerate dipole bands with similar energy
staggering and electromagnetic strengths have
been explained with aplanar tilted rotation of
the triaxial core along with the valence neutrons and protons aligned along the two extreme axes of the core. Recently, Relativistic Mean Field (RMF) calculations predicted
multiple chiral bands in some of the odd odd
isotopes of Ag, Rh and In, owing to their triaxial shape. The truncated shell model calculations prescribe an alternative angular momentum coupling scheme, namely, the chopstick model to explain these bands.
Several theoretical approaches have been
used to probe the chiral doublet band structures observed in odd odd nuclei.
most of the studies, particle-rotor and threedimensional cranking approaches have been
employed to interpret the observed chiral band
structures. Although, these models have been
∗ Electronic
address: [email protected]
quite successful to provide some basic understanding of the doublet bands, they have also
exhibited some deficiencies. In the present
work, we shall provide a detailed investigation
of 102 Ag using the microscopic triaxial projected shell model (TPSM) approach [3]. The
doubly odd nucleus 102 Ag can provide information on different modes of coupling mechanisms between the odd proton and the odd
neutron outside the 100 Sn core. By the powerfull detector array the above mentioned features can be studied.
Experimental details
Excited states in the 102 Ag nucleus were
populated in the 75 As(31 P, p3n)102 Ag fusionevaporation reaction at Elab = 125 MeV. The
de-excitations were investigated through inbeam gamma-ray spectroscopic techniques.
The 31 P beam was provided by the PelletronLINAC facility at TIFR, Mumbai. The 75 As
target of thickness 2.8 mg/cm2 was prepared
by vacuum evaporation and rolled onto a
10 mg/cm2 thick Pb backing. The recoiling nuclei in the excited states were stopped
within the target and the de-exciting gammarays were detected using the Indian National
Gamma Array (INGA) consisting of 21 Compton suppressed clover detectors. Two and
higher fold clover coincidence events were
recorded in a fast digital data aquisition system based on Pixie-16 modules of XIA LLC
[4]. The data sorting routine “Multi pARameter time stamped based COincidence Search
program (MARCOS)”, developed at TIFR,
sorts the time stamped data to generate Eγ Eγ matrices and Eγ -Eγ -Eγ cubes compatible
with Radware format.These data were used to
develop the level scheme.
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Proceedings of the DAE Symp. on Nucl. Phys. 59 (2014)
FIG. 1: Comparison of the measured energy levels of negative parity yrast and excited bands for
with those from TPSM calculation.
The present level scheme of 102 Ag is built
on the I = 5+ ground state. The level scheme
has been extended substantially with addition
of about fifty new transitions to the earlier
reported ones [5, 6]. The level scheme is established up to ∼ 10 MeV excitation energy.
The present level scheme preserves major features of the previously observed bands by S.
Rastikerdar [5] and V. Ravi Kumar et al.[6].
Previously reported level at 2378 keV having 4 τ <4ns has not been observed in the
present work. A new band consisting of 261-,
275-, 237-, and 267- keV transitions has been
observed. The states of this band decay to
yrast band by various gamma rays that have
been observed in the present work. The projected basis are employed to diagonalize the
shell model Hamiltonian consisting of pairing plus quadrupole -quadrupole interaction
terms. The projected energies, obtained after shell model diagonalization, for the doublet bands in doubly odd nucleus 102 Ag are
depicted and compared with the corresponding experimental data in Fig. 1.
Authors acknowledge the joint effort of
IUAC, New Delhi, TIFR, Mumbai, and IUCDAEF and SINP, Kolkata, in establishing
the INGA clover array. Financial support
from IUAC, New Delhi, under the Centre
of Advanced Study Funds, and UGC, New
Delhi, is duly acknowledged.
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[3] Y. Sun, J.A. Sheikh, G.-L. Long, Phys.
Lett. B 533, 253(2002)
[4] R. palit et al., Nucl. Instrum. Methods A
90, 680 (2012).
[5] S. Rastikerdar, Physics of Atomic Nuclei,
64, 1210(2001).
[6] V. Ravi. Kumar et al., Z. Phys. A 351,
249 (1995).
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