The origin of diffuse interstellar bands (DIBs) has been controversial for many years. Recently, it was demonstrated that the two DIBs at 9,577 Å and 9,632 Å could be explained by electronic transitions of the C60+ ion. However, the origin of these two electronic transitions are not completely understood. We performed the density functional theory calculations to optimize the structure of C60+ in D5d symmetry, which resulted from the ejection of an electron out of the icosahedral C60. The excitation energies from the ground electronic state to the seven lowest excited states, as well as corresponding oscillator strengths were calculated using the time-dependent density functional theory. The results indicate that the transition from the ground A1u state to the doubly degenerate E1g state is the lowest energy transition with non-zero oscillator strength. The spin-orbit coupling and/or the Jahn-Teller distortion could remove the degeneracy of the E1g excited state and provide an explanation for the two close energy DIBs assigned to C60+. We test this hypothesis using the complete active space self-consistent field (CASSCF) method with the 17 electron and 9 orbital active space followed by the multireference perturbation theory calculations.

Nature of two diffuse interstellar bands revealed by electronic transitions in C60+

253rd National Meeting (2017)

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