Collision echo in magnetic field

The effects of the longitudinal magnetic field on the collision photon echo, which is formed by two laser pulses with orthogonal polarizations on the transition with the angular momentum change Ja = 0 → Jb = 1 and arises due to the action of the elastic depolarizing collisions, are studied theoretically. It is shown that weak magnetic field acts to diminish the intensity of the collision echo up to zero, providing the tools for measuring the relaxation rates due to such collisions. With the further increase of the magnetic field strength the echo intensity reveals almost pure harmonic oscillations, though in strong magnetic field the echo appears not due to the action of collisions but mainly due to the action of the magnetic field, so it becomes not collision but conventional photon echo. However the comparison of the amplitudes of the collision echo in zero magnetic field with the maximum echo amplitude in strong magnetic field yields one more way to measure the relaxation rates due to elastic depolarizing collisions. (© 2011 by Astro Ltd., Published exclusively by WILEY‐VCH Verlag GmbH & Co. KGaA) (© 2011 by Astro Ltd., Published exclusively by WILEY‐VCH Verlag GmbH & Co. KGaA)