Orientation and alignment echoes

• Published in: Physical review letters Vol. 114; no. 15; p. 153601
• Main Authors: Karras, G, Hertz, E, Billard, F, Lavorel, B, Hartmann, J-M, Faucher, O, Gershnabel, Erez, Prior, Yehiam, Averbukh, Ilya Sh
• Format: Journal Article
• Language: English
• Published: United States American Physical Society 17-04-2015
• Subjects: Alignment; Atomic and Molecular Clusters; Atomic Physics; Carbon dioxide; Collection; Echoes; Excitation; Femtosecond; Lasers; Optics; Orientation; Physics
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.114.153601

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 CO_{2} molecules excited by a pair of femtosecond laser pulses.