Dynamic simulation study on ultrafast excited-state torsional dynamics of 9,9′-bianthryl (BA) in gas phase: Real-time observation of novel oscillation behavior with the torsional coordinate

Detailed dynamic simulation study on the excited-state torsional dynamics of the gas phase 9,9′-bianthryl (BA) following photoexcitation to its S1 state by a femtosecond laser pulse has been reported for the first time. The novel oscillation behavior with the torsional coordinate between the two symmetric potential minima of the S1 state is observed by real-time monitoring dihedral angles formed by the two anthracene moieties. The dihedral angles are twisted between 60° and 120°. At the same time, the central C–C bond is shortened following the conformational torsion. Our simulation results are in good agreement with the previous spectroscopic studies.