Recently, some of us reviewed and studied the photoionization dynamics of C₆₀ that are of great interest to the astrochemical community as four of the diffuse interstellar bands (DIBs) have been assigned to electronic transitions in the C₆₀$^+$ cation. Our previous analysis of the threshold photoelectron spectrum (TPES) of C₆₀ [Hrodmarsson et al., Phys. Chem. Chem. Phys. 22, 13880–13892 (2020)] appeared to give indication of D_3d$^+$ ground state symmetry, in contrast to theoretical predictions of D_5d$^+$ symmetry. Here, we revisit our original measurements taking account of a previous theoretical spectrum presented in the work of Manini et al., Phys. Rev. Lett. 91(19), 196402 (2003), obtained within a vibronic model parametrized on density functional theory/local-density approximation electronic structure involving all h_g Jahn–Teller active modes, which couple to the $^2$H_u components of the ground state of the C₆₀$^+$ cation. By reanalyzing our measured TPES of the ground state of the C₆₀ Buckminsterfullerene, we find a striking resemblance to the theoretical spectrum calculated in the work of Manini et al., Phys. Rev. Lett. 91(19), 196402 (2003), and we provide assignments for many of the hg modes. In order to obtain deeper insights into the temperature effects and possible anharmonicity effects, we provide complementary modeling of the photoelectron spectrum via classical molecular dynamics (MD) involving density functional based tight binding (DFTB) computations of the electronic structure for both C₆₀ and C₆₀$^+$. The validity of the DFTB modeling is first checked vs the IR spectra of both species which are well established from IR spectroscopic studies. To aid the interpretation of our measured TPES and the comparisons to the ab initio spectrum we showcase the complementarity of utilizing MD calculations to predict the PES evolution at high temperatures expected in our experiment. The comparison with the theoretical spectrum presented in the work of Manini et al., Phys. Rev. Lett. 91(19), 196402 (2003), furthermore, provides further evidence for a DC_5d symmetric ground state of the C₆₀$^+$ cation in the gas phase, in complement to IR spectroscopy in frozen noble gas matrices. This not only allows us to assign the first adiabatic ionization transition and thus determine the ionization energy of C₆₀ with greater accuracy than has been achieved at 7.598 ± 0.005 eV, but we also assign the two lowest excited states ($^2E$_1u and $^2E$_2u) which are visible in our TPES. Finally, we discuss the energetics of additional DIBs that could be assigned to C₆₀$^+$ in the future.

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