Bond-path-rigidity and bond-path-flexibility of the ground state and first excited state of fulvene

Abstract

Here we have determined the precessions K and K’ of the {p,p′} and {q,q′} path-packets for the excited state deactivation reaction of fulvene in terms of bond-flexing, bond-torsion and bond-anharmonicity that includes the tendencies towards bond-path-rigidity and bond-path-flexibility. An asymmetry is found for the S1 state resulting in an unpredictable variation in the direction of the bond-path-rigidity as a function of the torsion coordinate. Uniquely, the S1 state at torsion θ = 0.0° possesses the possible maximum bond-path-rigidity, along the entire bond-path but then drops lower than for the S0 state at the conical intersection indicating photo-excitation facilitates the torsion.