Electron transfer and level crossing induce anomalous photoionization along halogen@C₆₀ series

Our earlier study finds that the photoionization properties of the configurations Cl⁻@C₆₀⁺, Br⁻@C₆₀⁺ and I⁻@C₆₀⁺ are insensitive to the C₆₀ level where the vacancy is formed following the electron transfer [1,2]. This is because, before the transfer, the neutral halogen np level is energetically above the 2p level of empty C₆₀, so the transfer induced screening separates the levels further. The situation is different if the free atomic level locates below 2pC₆₀ as is the case for the halogen F. In forming F⁻@C₆₀⁺, therefore, the screening from the transfer causes 2pF to rise and move toward 2pC₆₀ from below it. This creates the condition of a reduced level-separation leading to a crossing, instead of the increase as happens for other halogens. The effect sensitizes the atom-C₆₀ hybridization mechanism. As a result, the transfer of a hybrid versus a pure C₆₀ electron makes a difference [3]. Many body DFT calculations for the photoionization of pure and hybrid levels along this halogen series will be presented to showcase this novel but anomalous phenomenon.

References



[1] D. Shields et al., J. Phys. B 53, 125101 (2020).

[2] D. Shields et al., Euro. Phys. J. D 74, 191 (2020).

[3] E. Ali et al., J. Phys. B (2022), in press, 107061.R1.