First observation of Auger-process induced anharmonic oscillation in molecular systems under high-density excitation

Unusually intense overtones of three vibrational modes were found just after high-density excitation of phthalocyanine microcrystal film and they decay approximately with a power-law (t2) due to the Auger-type bi-excitonic quenching which induces anharmonic vibration. The decay is associated with vibrational relaxation in the lowest excited singlet state (exciton) after the internal conversion from a higher excited state (excited exciton). The observation of the high-frequency-overtone has become possible by feeding the higher vibrational levels by the Auger process, since small Franck-Condon factor do not allow population of the anharmonic vibrational levels by direct excitation.