Effect of variations of the magnetic field on the analytical signal of a magneto-optic rotation spectrometer employing a Faraday configuration

In this work, residual ripple on the 50 Hz mains smoothed power supply of an electromagnet was found to cause incidental magnetic field modulation of atomic magneto-optic rotation (AMOR) signals of analytes. The modulation occurs at 100 Hz, twice the 50 Hz mains frequency, and is observed on AMOR noise power spectra of copper, silver and magnesium as an interference peak at 100 Hz. A theoretical model is developed to explain the amplitude dependence of this 100 Hz interference on magnetic field strength. Experimental findings indicate that at low magnetic field strength dichroic effects mainly generate the interference peak, as the magnetic field strength increases birefringent effects perpetuate the interference peak frequency. The magnetic field used in this work was composed of a mainly DC component with a small superimposed AC ripple. The absorption profile of the analyte is split into two sigma absorption profile components. The effect of the AC magnetic field causes the sigma profiles to oscillate their overlap with the source emission profile at 100 Hz, giving rise to the peak frequency signal. This will lead to background-free signal measurements if a lock-in technique is additionally employed. The resulting improvement in signal-to-noise ratio will make the study of hyperfine structures feasible in AMOR spectrometer systems.