Speaker
Description
A.Biswas1,2, U. S. Ghosh1, B. Mukherjee1, S. Rai1,3, K. Mondal1, A.Chakraborty1,
A. Sharma4, S. Muralithar5, R. P. Singh5 and U. Dutta6
1Department of Physics, Siksha-Bhavana, Visva-Bharati, Santiniketan, Bolpur - 731235, India
2Department of Physics, A. M. College, Jhalda, Purulia – 723202, India
3Department of Physics, Salesian College, Siliguri Campus, Siliguri - 734001, India
4 Department of Physics, Himachal Pradesh University, Shimla - 171005, INDIA
5Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi - 110067, India
6 Saha institute of Nuclear Physics, Kolkata – 700064, India
Introduction
The structures of the odd-odd nuclei in mass region ≈70 attract more attention because both single particle and collective excitations with different shapes, namely prolate, oblate and tri-axial have been observed in this region. At low spins, properties of the nuclei are governed by 1f5/2, 2p3/2 and 2p1/2 spherical shell model orbitals. However , the high spin states and excitation energies are due to the particle-hole excitation from the 1f7/2 to 1g9/2 high-j intruder orbitals. In the odd-odd nucleus 70As, the low lying states were experimentally well investigated by the works of Brink et al. [1] and Filevich et al.[2] using proton, alpha and light-ions as projectile. The study of the high spin states of 70As, using 16O beam was done by Badika et al. [3] and they could populate up to 11+ and tentatively up to the 13+ state at 4.076 MeV. The lifetime measurements of 11+ and 13+ levels, by Garcia Bermudez et al. [4] indicated an enhancement in B(E2) values of the 981 keV and 1343 keV transitions. The work by B. Mukherjee et al[14], using HIRA+GDA at IUAC extended level scheme up to 8.9 MeV with tentative spin parity 19+. Authors have reported three rotational bands, with two positive parity bands which are the signature partners of each other. However the signature partner of the negative parity band could not be established in this work. To get more information about the nuclear structure of 70As, an experiment was performed using INGA array of 16 Compton suppressed HPGe clover detectors at IUAC, New Delhi.
Experiment and Analysis
Excited states in 70As were populated through in-beam γ-ray spectroscopic techniques using the 48Ti(28Si, αpn) fusion-evaporation reaction at a beam energy of 100 MeV. Emitted γ-rays of excited nuclei were detected in the γ-γ coincidence mode using 16 Compton suppressed Ge clover detectors of the Indian National Gamma Array (INGA). Few new transitions have been observed and are being placed in the level scheme. Spin and parity assignments are also in progress by extracting the DCO and Polarization asymmetry values of the γ-rays.
Acknowledgement
We would like to acknowledge Mr. S. R. Abhilash (IUAC) for target preparation and pelletron staff of IUAC for providing excellent beam.
References
[1] B.O. ten Brink, J. Akkermans and H. Verheul, Nucl. Phys. A330 (1979) 409.
[2] A. Filevich, M. Behar, G. Garcia Bermudez and M.A.J. Mariscotti, Nucl. Phys. A309 (1978) 285.
[3] T. Badika, V. Cojocaru, D. Pentelica, I. Popescu and N. Scintei, Nucl. Phys. A535 (1991) 425.
[4] G. Garcia Bermudez, J. Dӧring, G.D. Johns, R.A. Kaye, M.A. Riley, S.L. Tabor, C.J. Gross, M.J. Brinkman
and H.Q. Jin, Phys. Rev. C 56 (1997) 2869.
[5] B. Mukherjee et al., Acta Phys. Hung. N. S. 11, 305 (2000).
