The collision between a molecule and a solid surface lies at the heart of many processes. Examples include heterogeneous catalysis, fabrication of micro-electronic devices, astro-chemistry processes and even the heating of a space craft returning into the atmosphere. In all of these examples it is crucially important to understand the variables which determine whether the collision will be elastic or inelastic, whether the molecule will stick to the surface and whether it will dissociate into smaller fragments.
To study the collision processes controlled experiments are needed. One of the molecular properties which determine the collision outcome is the relative angle between the rotation axis of the molecule and the surface plane. Up to now, there have been only a few experiments where the rotational orientation of the molecule in a molecule-surface collision has been controlled and measured. In this paper, a new method is introduced for controlling and measuring the rotational orientation of a molecule before and after the collision with the surface. The method is based on controlling the quantum state of the molecule with magnetic fields. As a first application of this technique the collision of hydrogen molecules with various copper surfaces was studied.