• A K Jain

      Articles written in Pramana – Journal of Physics

    • Magnetic rotation – past, present and future

      A K Jain Deepika Choudhury

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      Magnetic-dipole rotational (MR) bands were discovered about 15 years ago without any theoretical prediction in contrast to the super-deformed (SD) bands which were predicted long ago. First identification of a quasirotational structure as MR band occurred around 1992 although Kr isotopes probably have the first set of data having the signatures of MR bands as shown by us. Our first compilation of MR bands listed 120 MR bands in 56 nuclides which have now grown to more than 180 bands in 80 nuclides. We have observed new MR bands in the $A = 130$ mass region in 137Pr,139Nd and 135Ba nuclei. This led to the observation of the smallest MR bands in 137Pr, multiple minima in the 𝛾 deformation in 135Ba, coexistence of band structure based on these minima and band crossing of MR bands in $A = 130$ region. Some of these results have been reviewed in this paper along with theoretical calculations. There are still a number of questions related to MR bands which have not been fully resolved. The role of neutrons/protons in magnetic rotation still needs to be delineated. Do the MR bands follow the $I(I + 1)$ behaviour? Are these structures as regular as normal rotational bands? How important is the existence of deformation for MR bands? We address some of these questions in this paper.

    • Systematic of signature inversion in $(h_{11/2})_{\text{p}}\otimes (i_{13/2})_{\text{n}}$ for odd–odd nuclei in rare-earth nuclei

      Kawalpreet Kalra Alpana Goel Sukhjeet Singh Sushil Kumar A K Jain

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      Systematic features of the signature inversion phenomenon in $(h_{11/2})_{\text{p}}\otimes (i_{13/2})_{\text{n}}$ in doubly-odd rare-earth nuclei are presented. These features are generally observed in high-$j$ orbitals, mainly, in $(h_{9/2})$, $(h_{11/2})$ and $(i_{13/2})$. Calculations are carried out within the framework of the two quasiparticle plus rotor model (TQPRM) to explain strong odd–even staggering and signature inversion observed in these high-$j$ orbitals. The shifting of point of inversion to lower/higher spin with the increase in neutron/proton numbers is well explained by the calculations. It is found that 1/2[541] proton orbital of $h_{9/2}$ is necessary in the lower mass region to obtain the point of inversion.

    • Predicting superdeformed rotational band-head spin in A ∼ 190 mass region using variable moment of inertia model

      V S Uma Alpana Goel Archana Yadav A K Jain

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      The band-head spin (𝐼0) of superdeformed (SD) rotational bands in 𝐴 ∼ 190 mass region is predicted using the variable moment of inertia (VMI) model for 66 SD rotational bands. The superdeformed rotational bands exhibited considerably good rotational property and rigid behaviour. The transition energies were dependent on the prescribed band-head spins. The ratio of transition energies over spin 𝐸𝛾/2𝐼 (RTEOS) vs. angular momentum (𝐼 ) have confirmed the rigid behaviour, provided the band-head spin value is assigned correctly. There is a good agreement between the calculated and the observed transition energies. This method gives a very comprehensive interpretation for spin assignment of SD rotational bands which could help in designing future experiments for SD bands.

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