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.