Abstract
We present one of the simplest classical systems featuring the echo phenomenon—a collection of randomly oriented free rotors with dispersed rotational velocities. Following excitation by a pair of time-delayed impulsive kicks, the mean orientation or alignment of the ensemble exhibits multiple echoes and fractional echoes. We elucidate the mechanism of the echo formation by the kick-induced filamentation of phase space, and provide the first experimental demonstration of classical alignment echoes in a thermal gas of molecules excited by a pair of femtosecond laser pulses.
- Received 27 January 2015
DOI:https://doi.org/10.1103/PhysRevLett.114.153601
© 2015 American Physical Society