A SINGLE-MOLECULE INTERFEROMETER FOR MEASUREMENT OF FEMTOSECOND LASER-PULSE DURATION

An electronic excitation of a molecule by a sequence of two femtosecon d phase-locked laser pulses is considered. In this case interference t akes place between the vibrational wave packets induced by each of the subpulses within a single molecule. It is shown that, due to the dyna mical squeezing effect of a molecular vibrational state, this interfer ence allows one to measure the duration of a femtosecond laser pulse. This can be achieved experimentally by measuring the dependence of the integral fluorescence of the excited molecule on the delay time betwe en the subpulses. The interference can lead to a sharp peak (or to a d ip) in that dependence, the width of which is equal to the duration of the laser pulse. It is shown that a finite temperature of the medium is favourable for such an experiment.