Ritika Garg

Fusion and transfer reactions around the Coulomb barrier for 28Si+90,94Zr systems

Fusion excitation functions and transfer probabilities were measured for 28Si+90,94Zr systems around the Coulomb barrier, using the recoil mass separator, Heavy Ion Reaction Analyzer (HIRA) at Inter University Accelerator Centre (IUAC), New Delhi. The aim of these experiments was the study of coupling effects of inelastic and transfer channels on the sub-barrier fusion cross section enhancement. The experimental fusion cross sections were found to be strongly enhanced as compared to one dimensional barrier penetration model (1-d BPM) predictions in both the cases. The trend of data could be easily reproduced theoretically using coupled channels code CCFULL in the case of 28Si+90Zr but the observed enhancement could not be explained in the case of 28Si+94Zr, which may be attributed to the coupling of multinucleon transfer channels as both isotopes have similar collective strengths. The transfer probabilities in the case of 94Zr were found to be substantially higher than for 90Zr in the sub-barrier region.

Dipole bands in high spin states of 57135La78

High spin states of 135La have been investigated using the reaction 128Te(11B,4n)135La at a beam energy of 50.5 MeV. Two negative parity dipole bands (ΔI = 1) have been established. Crossover E2 transitions have been observed for the first time in one of the dipole bands. For the Tilted Axis Cranking (TAC) calculations, a three-quasiparticle (3qp) configuration π(h11/2)1⊗ν(h11/2)−2 and a five-quasiparticle (5qp) configuration π(h11/2)1(g7/2/d5/2)2⊗ν(h11/2)−2 have been taken for the two negative parity dipole bands. The comparison of experimental observables with TAC calculations supports the configuration assignments for both the dipole bands.

Magnetic rotation (MR) band-crossing at high spin states: Role of nucleons in this crossing in N = 78 odd-Z isotones

Magnetic-dipole rotational (MR) bands were discovered about 15 years ago, and have been explained using shears mechanism. The theoretical understanding of these bands has been provided using tilted axis cranking (TAC). At present, magnetic rotation has been seen in whole nuclear landscape and about 180 bands in 80 nuclides has been observed in mass regions A=20, 60, 80, 110, 135 and 195 respectively. The crossing of these bands (ΔI = 1) is very much similar to normal band crossing (ΔI = 2) and already exhibited in different mass regions. We have observed new MR bands and their crossing in the A = 130 mass region in 135La, 137Pr and 139Pm nuclei. The systematic evolution of this phenomenon in N=78 odd-Z isotones leads us to understand the role on nucleons in this crossing.

Check for chirality in 102Rh

Excited states in 102Rh, populated by the fusion-evaporation reaction 94Zr(11B,3n)102Rh at a beam energy of 36 MeV, were studied using the INGA spectrometer at IUAC, New Delhi. The angular correlations and the electromagnetic character of some of the gamma-ray transitions observed were investigated in details. A new chiral candidate sister band was found in the level-scheme of 102Rh. Lifetimes of exited states in 102Rh were measured by means of the Doppler-shift attenuation technique. The experimental results do not support the presence of static chirality in 102Rh.

Enhanced 0{sub g.s.}{sup +}->2{sub 1}{sup +} E2 transition strength in {sup 112}Sn

Two consecutive Coulomb excitation experiments were performed to excite the 2{sub 1}{sup +} states of {sup 112,116}Sn using a {sup 58}Ni beam. For {sup 112}Sn a B(E2arrow up) value of 0.242(8) e{sup 2} b{sup 2} has been determined relative to the known value of {sup 116}Sn. The present value is more precise than previous measurements and shows a clear discrepancy from the expected parabolic dependence between the doubly magic nuclei {sup 100}Sn and {sup 132}Sn. It implies that the reduced transition probabilities are not symmetric with respect to the midshell mass A=116.