Optical properties of the vibrations in charged C$_{60}$ molecules

TL;DR

This study uses density functional theory to analyze the infrared vibrational properties of charged C60 molecules, revealing enhanced oscillator strengths for certain modes and challenging previous quadratic doping models.

Contribution

It provides a first-principles calculation of vibrational transition strengths in charged C60, showing deviations from earlier theoretical predictions.

Findings

Enhanced oscillator strengths for specific vibrational modes in charged C60

Good agreement with experimental 'giant resonances' observed

Contradicts previous quadratic doping dependence predictions

Abstract

The transition strengths for the four infrared-active vibrations of charged C$_{60}$ molecules are evaluated in self-consistent density functional theory using the local density approximation. The oscillator strengths for the second and fourth modes are strongly enhanced relative to the neutral C$_{60}$ molecule, in good agreement with the experimental observation of ``giant resonances'' for those two modes. Previous theory, based on a ``charged phonon'' model, predicted a quadratic dependence of the oscillator strength on doping, but this is not borne out in our calculations.