ORIENTING POLAR MOLECULES IN MOLECULAR BEAMS . SYMMETRIC TOPS

Symmetric-top molecules exist in various orientations in even very weak electric fields, in contrast to diatomic molecules which are oriented only in fields so large as to be impractical. For symmetric tops these orientations can be separated in an inhomogeneous electric field, and calculations are presented for the separating properties of a hexapole field. The transmission and the final distributions of velocity and orientations have been calculated for several different molecules over a range of conditions. Experimental transmission measurements were made and are in good agreement with calculations. By fitting experimental points to calculated transmission curves dipole moments in good agreement with literature values have been determined. The molecules separated by the hexapole field are experimentally shown to make adiabatic transitions into a homogeneous electric fieM, providing evidence that the molecules can be oriented in the laboratory reference frame.