Orientation and Alignment Echoes

Speaker: 
Ilya Averbukh, Weizmann Institute of Science
Event Date and Time: 
Thu, 2016-07-14 12:30 - 13:30
Location: 
Hennings 302
Local Contact: 
Valery Milner
Intended Audience: 
Graduate

 

Echoes are common in many areas of physics, including NMR, plasma physics, nonlinear optics, cavity quantum electrodynamics, cold atoms physics, and even high energy hadron beams experiments.

Recently we discovered (probably) the simplest classical system 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 in space and time.

I will describe the mechanism of the echo formation based on the kick-induced filamentation of the rotational phase space. Then I will provide the results of the first three experiments demonstrating different kinds of the alignment echoes in a gas of CO2 molecules excited by a pair of femtosecond laser pulses. The detection techniques included (i) laser-induced birefringence measurements, (ii) third harmonic generation, and (iii) coincidence Coulomb explosion imaging.

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