Chiral Molecular Motors Ignited by Femtosecond Pump−Dump Laser Pulses

The results of a theoretical study on a chiral molecular motor ignited by a femtosecond pump−dump laser excitation are presented. The rotational direction of the motor is determined by the gradient of the potential energy surface (PES) of the electronic excited state in the Franck−Condon region. The pump−dump ignition method is applied to (R)-2-methyl-cyclopenta-2,4-dienecarbaldehyde, which is one of the simplest chiral molecular motors. The aldehyde group is the engine of the chiral molecular motor. The magnitudes of the angular momentum of the rotational motion are quantum-mechanically evaluated. The motor dynamics is analyzed in terms of the rotational wave packet propagation on the ground-state PES. A time-frequency-resolved photoionization method for observing the motor dynamics in real time is also described.