Impact of helium isotopic mass on the mobility of CO + ions

Abstract The MMA2V and MMA2Q approaches, previously developed within a classical framework [Eur. Phys. J. D 79, (2025)], are extended here to a fully quantum-mechanical treatment to investigate the transport properties of CO + ions in helium isotopes. Particular emphasis is placed on the low-temperature regime, where quantum effects become significant. Quantum-mechanical momentum-transfer cross sections are computed and used to evaluate the reduced ion mobility in both 4 He and 3 He buffer gases. The analysis focuses on isotope-dependent effects arising from the variation of the reduced mass, and their influence on collision dynamics and transport behavior. The calculated mobilities show improved agreement with available experimental data compared to classical predictions, especially in the intermediate-and high-field regimes, with the MMA2V approach providing the most accurate overall description. These results provide a quantitative assessment of isotope effects in ion-helium systems and highlight the importance of quantum-mechanical treatments for reliable modeling of ion transport in low-temperature gases.