Speaker
Description
High-resolution experiments using cryogenic trap-based positron beams have recently advanced the understanding of positron-molecule interactions in two distinct but complementary areas: the precise determination of binding energies in polyatomic molecules and unraveling resonant annihilation mechanisms. In this talk, I will present recent progress in these areas, with a specific focus on annihilation dynamics that extend beyond the standard vibrational Feshbach resonance (VFR) model. Unlike polar molecules, where binding is mediated by permanent dipole interactions, binding in non-polar systems is driven by strong electron-positron correlations, manifesting as virtual positronium formation within the molecular field [1]. Regarding annihilation resonances, while traditional models rely on fundamental vibrational modes, recent studies demonstrate that this picture is insufficient [2, 3]. The identification of discrete annihilation resonances driven by multi-quantum vibrational excitations (combinations and overtones) provides a unique probe of Intramolecular Vibrational Redistribution (IVR) [4]. The broader implications of these findings for refining many-body theoretical frameworks and understanding positron processes in astrophysical environments will be discussed.
*This work is a collaboration with J. R. Danielson, E. Arthur-Baidoo, C. M. Surko (UC San Diego, USA), and A. Mundaplackal (Ahmedabad University, India).
[1] J. R. Danielson, S. Ghosh, E. Arthur-Baidoo, D. R. Witteman, and C. M. Surko, Phys. Rev. A. 108, 032801 (2023).
[2] S. Ghosh, J. R. Danielson, and C. M. Surko, Phys. Rev. Lett., 125, 173401 (2020).
[3] S. Ghosh, J. R. Danielson, and C. M. Surko, Phys. Rev. Lett., 129, 123401 (2022).
[4] A. Mundaplackal, S. Ghosh, J. R. Danielson, E. Arthur-Baidoo, and C. M. Surko, Phys. Rev. A, (Accepted Jan 15, 2026).
