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Your search keyword '"Wahid, S. G."' showing total 11 results
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11 results on '"Wahid, S. G."'

1. Emergence of an island of extreme nuclear isomerism at high excitation near $^{208}$Pb

Author

Wahid, S. G., Tandel, S. K., Suman, Saket, Srivastava, P. C., Kumar, Anil, Chowdhury, P., Kondev, F. G., Janssens, R. V. F., Carpenter, M. P., Lauritsen, T., Seweryniak, D., and Zhu, S.

Subjects
Nuclear Experiment
Abstract

Metastable states with T$_{1/2}$ = 8(2) ms in $^{205}$Bi and T$_{1/2}$ = 0.22(2) ms in $^{204}$Pb, with $\approx $ 8 MeV excitation energy and angular momentum $\ge $ 22 $\hbar $, have been established. These represent, by up to two orders of magnitude, the longest-lived nuclear states above an excitation energy of 7 MeV, ever identified in the nuclear chart. Additionally, the half-life of the 10.17 MeV state in $^{206}$Bi has been determined to be 0.027(2) ms, the next highest value in this highly excited regime. These observations indicate the emergence of an island of extreme nuclear isomerism arising from core-excited configurations at high excitation in the vicinity of the doubly closed-shell nucleus $^{208}$Pb. These results are expected to provide discriminating tests of the effective interactions used in current large-scale shell-model calculations., Comment: 17 pages, 5 figures

Published
2022
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2. Isomers in 203Tl and core excitations built on a five-nucleon-hole structure

Author

Bothe, V., Tandel, S. K., Wahid, S. G., Srivastava, P. C., Bhoy, Bharti, Chowdhury, P., Janssens, R. V. F., Kondev, F. G., Carpenter, M. P., Lauritsen, T., Seweryniak, D., and Zhu, S.

Subjects
Nuclear Experiment
Abstract

Isomers with three- and five-nucleon-hole configurations have been established in $^{203}$Tl. These include newly identified levels with a three-nucleon structure: {\it I}$^{\pi }$ = (15/2$^{-}$) with {\it T}$_{1/2}$ = 7.9(5) ns, and {\it I}$^{\pi }$ = (35/2$^{-}$) with {\it T}$_{1/2}$ = 4.0(5) ns. In addition, five-quasiparticle states: {\it I}$^{\pi }$ = (39/2$^{-}$) with {\it T}$_{1/2}$ = 1.9(2) ns, and {\it I}$^{\pi }$ = (49/2$^{+}$) with {\it T}$_{1/2}$ = 3.4(4) ns have also been established. The previously determined long-lived decay [{\it T}$_{1/2}$ = 6.6(3) $\mu $s from this work] is associated with isomerism of the {\it I}$^{\pi }$ = (29/2$^{+}$) state. Levels above this long-lived isomer have been identified through a delayed-prompt coincidence measurement. Five-nucleon-hole states with excitation energies {\it E}$_{x}$ $\approx $ 7 MeV have been established as well as possible octupole excitations of the $^{208}$Pb core built on these levels. The level scheme of $^{203}$Tl is extended up to {\it E}$_{x}$ $\approx $ 11 MeV with the inclusion of 25 new transitions. Empirical and shell-model calculations have been performed to aid in the description of the observed states which are found to be predominantly of intrinsic character., Comment: 14 pages, 10 figures

Published
2021
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6. Nanosecond isomers and the evolution of collectivity in stable, even- A Hg isotopes

Author

Suman, Saket, primary, Tandel, S. K., additional, Kumawat, Ankit, additional, Wahid, S. G., additional, Hemalatha, M., additional, Chowdhury, P., additional, Janssens, R. V. F., additional, Carpenter, M. P., additional, Khoo, T. L., additional, Kondev, F. G., additional, Lauritsen, T., additional, Lister, C. J., additional, Seweryniak, D., additional, and Zhu, S., additional

Published
2021
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7. Study of signature inversion in 123,125I using Particle Rotor Model calculations.

Author

Lamani, Umakant, Das, Pragya, and Wahid, S. G.

Subjects
NUCLEAR shapes, ROTORS, PROBABILITY theory, CHROMOSOME inversions
Abstract

The phenomenon of signature inversion in positive parity yrast states of 123,125I nuclei has been studied using the Particle Rotor Model (PRM) calculations. The experimentally observed signature inversion is well reproduced from the PRM calculations. The change in the value of a triaxial parameter (γ) was observed after the inversion. The PRM calculations were also used to describe the reduced transition probabilities. The derived change in the value of " γ " (in Lund convention) after inversion is interpreted as the change in nuclear shape from near triaxial to tending towards noncollective oblate. [ABSTRACT FROM AUTHOR]

Published
2021
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8. Structure of odd- A Pt isotopes along the line of stability

Author

Wahid, S. G., primary, Tandel, S. K., additional, Chowdhury, P., additional, Janssens, R. V. F., additional, Carpenter, M. P., additional, Khoo, T. L., additional, Kondev, F. G., additional, Lauritsen, T., additional, Lister, C. J., additional, Seweryniak, D., additional, Zhu, S., additional, Chen, Q. B., additional, and Meng, J., additional

Published
2019
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9. Rotation-aligned isomer and oblate collectivity inPt196

Author

Wahid, S. G., primary, Tandel, S. K., additional, Chowdhury, P., additional, Janssens, R. V. F., additional, Carpenter, M. P., additional, Khoo, T. L., additional, Kondev, F. G., additional, Lauritsen, T., additional, Lister, C. J., additional, Seweryniak, D., additional, and Zhu, S., additional

Published
2015
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10. Rotation-aligned isomer and oblate collectivity in 196Pt.

Author

Wahid, S. G., Tandel, S. K., Chowdhury, P., Janssens, R. V. F., Carpenter, M. P., Khoo, T. L., Kondev, F. G., Lauritsen, T., Lister, C. J., Seweryniak, D., and Zhu, S.

Subjects
*ISOMERS, *NILSSON model, *GRAVITATIONAL potential, *ANGULAR momentum (Nuclear physics), *OBLATENESS constant, *NUCLEAR isospin
Abstract

An oblate rotational sequence, built on an aligned, two-quasineutron isomeric state has been established in 196Pt. The isomer has a half-life of 7.7(7) ns and is associated with the Iπ = 12+, (i13/2)² neutron configuration. Excited states, with angular momentum generated primarily through successive nucleon alignments, have been populated through 1p transfer from 197Au. The nucleus 196Pt is the most neutron-rich Pt isotope for which high-spin states, beyond the 12+ isomeric state, have been established thus far. Cranked shell model calculations have been performed to understand shape evolution with spin, and the role of nucleons occupying specific Nilsson orbitals in generating aligned angular momentum for both prolate and oblate deformations has been explored. [ABSTRACT FROM AUTHOR]

Published
2015
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11. Parity doublet structures in doubly-odd 216Fr.

Author

Pragati, Deo, A. Y., Tandel, S. K., Bhattacharjee, S. S., Chakraborty, S., Rai, S., Wahid, S. G., Kumar, S., Muralithar, S., Singh, R. P., Bala, Indu, Garg, Ritika, and Jain, A. K.

Subjects
*FRANCIUM, *NEUTRONS
Abstract

Parity doublet structures are established in 216Fr, which lies at the lower boundary of enhanced octupole collectivity in the trans-lead region. The newly identified levels are established as the simplex partner of a previously reported band leading to parity doublets with small (~55 keV) average energy splitting, a feature typical of nuclei with near-static octupole deformation. The observed levels do not follow a regular pattern of rotational bands, indicating low quadrupole collectivity. However, enhanced octupole correlations are evident from the small energy splitting and large B(E1)/B(E2) values. Staggering in E1 transition energies and B(E1)/B(E2) ratios is noted. The enhancement of octupole correlations in 216Fr is attributed to the availability of a neutron orbital with a K = 3/2 component. [ABSTRACT FROM AUTHOR]

Published
2018
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