Photodissociation of ICI molecule oriented by an intense electric field:: Experiment and theoretical analysis

The idea of orienting molecules by applying an intense electric field on a rotationally very cold molecular beam has been introduced in 1990 by Loesch and Remscheid (J. Chem. Phys. 1990, 93, 4779) and also by Friedrich and Herschbach (Z. Phys. D 1991, 18, 153). Here we describe an experiment in which the orientation thus produced in ICl molecules is tested by a photodissociation experiment. The paper discusses the orientation process with emphasis on the effects nonlinear in the applied electric field. The characterization of the oriented beam and the experiment will be briefly described. A complete simulation leads to a very good fit of the observed signal, but the rotational temperature deduced from this fit is higher than given by a direct measurement, the discrepancy being due to the presence of van der Waals complexes. This experiment has provided the first direct measurement (Clem. Phys. Lett. 1995, 244, 195) of the sign of the dipole of ICl (I(+)C1(-) as expected) and 3 measurement of the strong orientation achieved.