Abstract

To investigate orientational relaxation of molecules at the air/liquid interfaces we have used the technique of second harmonic generation as the probe. The idea of the experiment is to use a polarized picosecond pump pulse to preferentially excite molecules of a given orientation at the interface and thereby disturb the equilibrium orientational distribution. The relaxation of the perturbed distribution is monitored by the second harmonic signal generated by a time-delayed second laser pulse at the interface. Such surface second harmonic signal continues to change as the ground and excited molecules undergo rotation towards their equilibrium distributions and as the excited molecules relax back to the ground state.

© 1992 The Author(s)