Molecular Vibrations in Liquids: Direct Measurement of the Molecular Dephasing Time; Determination of the Shape of Picosecond Light Pulses

Molecular vibrations are coherently excited by an intense light pulse of duration ${t}_{p}$. The rise and decay of the vibrational amplitude is measured with delayed pulses of the same time dependence. The molecular dephasing time $\ensuremath{\tau}$ is obtained when $\ensuremath{\tau}\ensuremath{\gtrsim}{t}_{p}$, while the shape of the light pulse is found for $\ensuremath{\tau}\ensuremath{\ll}{t}_{p}$.