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The level lifetimes have been measured for a Shears band of $^{108}$Cd which exhibits bandcrossing. The observed level energies and B(M1) rates have been successfully described by a semi-classical geometric model based on shear mechanism. In this geometric model, the bandcrossing in Shears band has been described as the reopening of the angle between the blades of a shear.
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A dipole sequence has been observed and investigated in the 143 Sm nucleus populated through the heavy-ion induced fusion-evaporation reaction and studied using the Indian National Gamma Array (INGA) as the detection system. The sequence has been established as a Magnetic Rotation (MR) band primarily from lifetime measurements of the band members using the Doppler Shift Attenuation Method (DSAM). A configuration based on nine quasiparticles, with highly asymmetric angular momentum blades, has been assigned to the shears band in the light of the theoretical calculations within the framework of Shears mechanism with the Principal Axis Cranking (SPAC) model. This is hitherto the maximum number of quasiparticles along with the highest asymmetricity associated with a MR band. Further, as it has followed from the SPAC calculations, the contribution of the core rotation to the angular momentum of this shears band is substantial and greater than in any other similar sequence, at least in the neighbouring nuclei. This band can thus be perceived as a unique phenomenon of shears mechanism in operation at the limits of quasiparticle excitations, as manifested in MR band-like phenomena, evolving into collectivity.
Excited states of the neutron deficient $^{103}$Cd nucleus have been investigated via the $^{72}$Ge($^{35}$Cl, p3n) reaction at beam energy of 135 MeV by use of in-beam spectroscopic methods. Gamma rays depopulating the excited states were detected using the Gammasphere spectrometer with high-fold $gamma$-ray coincidences. A quadrupole $gamma$-ray coincidence analysis ($gamma^{4}$) has been used to extend the known level scheme. The positive parity levels have been established up to $J = 35/2hbar$ and $E_{x} = 7.071$ MeV. In addition to the observation of highly-fragmented level scheme belonging to the positive-parity sequences at E$_{x}sim$ 5 MeV, the termination of a negative-parity sequence connected by $E2$ transitions has been established at $J = 47/2 hbar$ and $E_{x} = 11.877$ MeV. The experimental results corresponding to both the positive- and negative-parity sequences have been theoretically interpreted in the framework of the core particle coupling model. Evidence is presented for a shape change from collective prolate to non-collective oblate above the $J^{pi} = 39/2^{-}$ (8011 keV) level and for a smooth termination of the negative-parity band.
The heaviest N=Z doubly-magic nucleus, $^{100}$Sn, and the neighboring nuclei offer unique opportunities to investigate the properties of nuclear interaction in extreme conditions. In particular, the Cd isotopes are expected to present features similar to those found in the Sn isotopic chain, since they have only two proton holes in the Z=50 shell. In this manuscript, the lifetime measurements of low-lying states in the even-mass $^{102-108}$Cd is presented. Thanks to the powerful detection capabilities of AGATA array and VAMOS++ spectrometer, the unusual employment of multi-nucleon transfer reactions permitted to investigate the first 2$^+$ and 4$^+$ states in all these nuclei, together with various deformed bands in $^{106}$Cd. The results were interpreted in the context of new state-of-the-art beyond-mean-field calculations, using the symmetry-conserving configuration-mixing approach. Despite the similarities in the electromagnetic properties of the low-lying states, there is a fundamental structural difference between the ground-state bands in the Z=48 and Z=50 isotopes. The comparison between experimental and theoretical results revealed a rotational character of the Cd nuclei, which have prolate-deformed ground states with $beta_2 approx 0.2$. At this deformation Z=48 becomes a closed-shell configuration, which is favored with respect to the spherical one.
High spin states of neutron deficient Trans-Lead nucleus $^{204}$At were populated up to $E_x sim 8,{rm MeV}$ through the $^{12}$C + $^{197}$Au fusion evaporation reaction. Decay of the high spin states including prompt and delayed gamma ray emission were studied to understand the underlying nuclear structure. The level scheme, which was partly known from earlier studies, was extended further through our experiment and analysis of spin and parity of the associated levels. An isomeric $16^+$ level $(tau=52(5), {rm ns})$, corresponding to $M2$ transition, was established from our measurements. Attempts were made at interpretation of the excited states based on multi quasiparticle and hole structure involving $2f_{5/2}$, $1h_{9/2}$, and $1i_{13/2}$ shell model states, along with moderate core excitation. Magnetic dipole band structure over the spin parity range:~$16^+ - 23^+$, which was found in the earlier Gammasphere study, was confirmed and explored in more detail, including the missing cross-over $E2$ transitions. Band-crossing along the shears band was observed and compared with the evidence of similar phenomena in the neighboring neutron deficient $^{202}$Bi, $^{205}$Rn isotones and the neighbouring $^{203}$At isotope. Based on comparison of the measured $B(M1)/B(E2)$ values for transitions along the band with the semiclassical model based estimates, the shears band of $^{204}$At was firmly established along with the level scheme.
The superdeformation and hyperdeformation in $^{108}$Cd have been studied for the first time within the framework of the fully self-consistent cranked mean field theory, namely, cranked relativistic mean field theory. The structure of observed superdeformed bands 1 and 2 have been analyzed in detail. The bumps seen in their dynamic moments of inertia are explained as arising from unpaired band crossings. This is contrary to an explanation given earlier within the framework of projected shell model. It was also concluded that this nucleus is not doubly magic SD nucleus.
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