LASER ZEEMAN AND NMR SPECTROSCOPY: EFFECTIVE TORQUE AND LASER LARMOR PRECESSION

Abstract

Laser Zeeman effects are caused by optical rectification in an electromagnetic field, in close formal analogy with the well known effects of static magnetic flux density (B). The conjugate product (Π) and dynamic molecular polarisability vector (iα″) form a torque formally analogous to that between the molecular magnetic dipole moment (m) and B. This defines the Larmor frequency of precession, which is shown to be directly proportional to the square of the electric field strength (E0, in volt m −1) of the laser through a molecular constant analogous to the gyromagnetic ratio. Supercomputer simulation is used to show that this torque generates distinctive new ensemble averages (time cross correlation functions) which mediate the onset of circular birefringence and dichroism ("magnetic" optical activity). Resonance in the presence of a co-axial magnetic field leads to "laser NMR" effects, which are created simply in terms of the torque and Larmor precession.