The effect of circularly polarized light on NMR spectra

Atoms and molecules subjected to a constant circularly polarized light beam carry a time-independent current density proportional to the intensity. The direction of the current is opposite for right and left polarization. As a result there is an induced magnetic moment, which is the inverse Faraday effect, and a magnetic field at a nucleus. Formulae are derived for the current density and the induced magnetic field at a nucleus; an equivalence is established between this field and the antisymmetric polarizability resulting from the nuclear magnetic moment. The shifts in the NMR frequencies of H-1, C-13, F-19 and Tl-205 due to a continuous-wave 10 W cm(-2) beam are estimated to be 0.2 to 50 mu Hz for right circular polarization at transparent wavelengths, with larger shifts for near-resonance conditions. If the full width at half maximum height of an electric-dipole allowed transition were 10 cm(-1), the circularly Polarized radiation at resonance would cause shifts of the order of a few hundred hertz for F-19. Shifts are expected for all magnetic nuclei. In a beam of sodium atoms the 10 W cm(-2) circularly polarized light, whose frequency is 6 GHz from resonance with a yellow D line, is predicted to induce an NMR shift of the order of 1 MHz.