Figure 2.

Model of the reaction dynamics for the trifluorinated indolylfulgide. a) Ring-opening and ring-closure reaction. Excitation of the closed form by visible light populates the Franck-Condon state. From hereon a first excited state reaction occurs on the time scale of 200 fs. The excited electronic state is left on a timescale of 9 ps. This process is related to the reformation of the electronic ground state of the closed form and to the ring-opening reaction to the open Z-form. When the open Z-form is excited by near ultraviolet light at 400 nm one observes S₁ reaction dynamics and a fast formation of the ground state of indolylfulgides in the open and the closed form on a < 1 ps timescale. b) Ring-opening reaction starting from a vibrational excess population produced by a preceding ring-closure reaction. Here the excess population produced in a UV pre-excitation process may be transferred by a second visible excitation pulse to the excited electronic state where it may influence further reaction dynamics.