Coexistence of single particle and collective excitation in $^{61}$Ni

• Main Authors: Bhattacharya, Soumik, Tripathi, Vandana, Rubino, E, Ajayi, Samuel, Baby, L. T, Benetti, C, Lubna, R. S, Tabor, S. L, Döring, J, Utsuno, Y, Shimizu, N, Almond, J. M, Mukherjee, G
• Format: Journal Article
• Language: English
• Published: 01-03-2023
• Subjects: Physics - Nuclear Experiment; Physics - Nuclear Theory
• DOI: 10.48550/arxiv.2303.00588

PhysRevC.054311 (2023) 107 The high spin states in 61 Ni have been studied using the fusion evaporation
reaction, Ti( $^{14}$C,3n) $^{61}$Ni at an incident beam energy of 40 MeV. A
Compton suppressed multi-HPGe detector setup, consisting of six Clover
detectors and three single crystal HPGe detectors was used to detect the
de-exciting $\gamma$ rays from the excited states. The level scheme has been
extended up to an excitation energy of 12.8 MeV and a tentative J$_{\pi}$ =
35/2$^+$ . The low-lying negative parity levels are found to be generated by
single particle excitation within the f p shell and also excitations to the
g$_{9/2}$ orbitals as explained well with shell model calculations using the
GXPF1Br+V M U (modified) interaction. Two rotational structure of regular E2
sequences with small to moderate axial deformation have been established at
higher excitation energy. Most interestingly, two sequences of M1 transitions
are reported for the first time and described as magnetic rotational bands. The
shears mechanism for both the bands can be described satisfactorily by the
geometrical model. The shell model calculation involving the cross shell
excitation beyond the fp shell well reproduce the M1 and E2 sequences. The
shell model predicted B(M1) values for the magnetic rotational band B1 show the
decreasing trend with spin as expected with closing of the shears.