Excited state positronium formation from C$_{\mathrm{60}}$ and C$_{\mathrm{240\thinspace }}$molecules

There exists a broad landscape of positronium (Ps) formation studies by implanting positron beams on atoms, molecules, polymers, solids, liquids, surfaces/films, metal-organic-frameworks and embedded nanostructures. Recently, ground state Ps formation studies using the C$_{\mathrm{60}}$ molecule as a target have been carried out [1,2]. Due to the dominant electron capture from the fullerene shell region and the spatial dephasing across the shell-width, a powerful diffraction effect was found to underpin the process of Ps formation in C$_{\mathrm{60}}$. In the current work, we access excited state Ps formations from both C$_{\mathrm{60}}$ and C$_{\mathrm{240}}$ fullerenes. Results reveal significant structures in the cross section as a function of both the impact energy and the Ps level -- structures that arise from positron-fullerene short-range interactions. Fullerenes are modeled by a local-density approximation (LDA) approach [3] and the Ps formation is treated by the continuum distorted-wave final-state (CDW-FS) approximation [4]. The work may motivate application of the Ps formation spectroscopy to gas phase nanoparticles and access fullerene-level- as well as Ps-level-differential measurements. [1] Hervieux et al., Phys. Rev. A \textbf{95}, 020701 (R) (2017); [2] Chakraborty et al., J. Phys.: Conf. Series \textbf{875}, 072002 (2017); [3] Choi et al., Phys. Rev. A \textbf{95}, 023404 (2017); [3] Fojon et al., Phys. Rev. A \textbf{54}, 4923 (1996).