Two-photon absorption: transitions induced in highly symmetric molecules by a magnetic field

It has recently been shown that certain two-photon transitions can be indiced in atoms by applying a static magnetic field at the intersection of two crossed laser beams. The mechanism involves quantum mechanical interference between different excitation pathways. In this letter it is shown that a similar effect takes place in any highly symmetric molecule such as methane or sulphur hexafluoride belonging to a cubic symmetry group. However, in this case, the effect occurs through a non-linear magneto-optical interaction which is quite distinct from the interference mechanism.