First investigation on the isomeric ratio in multinucleon transfer reactions : Entrance channel effects on the spin distribution

The multinucleon transfer (MNT) reaction approach was successfully employed for the first time to measure the isomeric ratios (IRs) of 211Po isomer (25/2+) and its ground state (9/2+) at the IGISOL facility using a 945 MeV 136Xe beam impinged on 209Bi and natPb targets. The dominant production of isomers compared to the corresponding ground states was consistently revealed in the 𝛼-decay spectra. Deduced IR of 211Po populated through the 136Xe+natPb reaction was found to have an enhancement of ≈1.8-times than that observed for the 136Xe+209Bi. State-of-the-art Langevin-type model calculations have been utilized to estimate the spin distribution of an MNT residue. The computations qualitatively corroborate with the considerable increase in the IRs of 211Po produced from 136Xe+natPb compared to 136Xe+209Bi. Theoretical investigations indicate a weak dependence of target spin on the IRs. The enhancement of the 211Po isomer in the 136Xe+natPb over 136Xe+209Bi can be attributed to the different proton (𝑝)-transfer production routes. Estimations demonstrate an increment in the angular momentum transfer, favorable for isomer production, with increasing projectile energy. Comparative analysis reveals the two entrance channel parameters, projectile mass and 𝑝-transfer channels, strongly influencing the population of the high-spin isomer of 211Po (25/2+). This letter reports the first experimental and theoretical study on the IRs of nuclei formed from two different 𝑝-transfer channels via two independent MNT reactions.