When a paramagnetic gas is placed in a magnetic field it becomes "circularly birefringent," that is, the vapor has different indices of refraction for left- and right-circularly polarized light. For light which is initially linearly polarized, the different indices of refraction lead to a rotation of the plane of polarization of light which is dependent on the magnetic field strength and the pathlength. Magnetic rotation spectroscopy is a technique in which this polarization rotation can be analyzed and related to various experimental parameters, such as atomic density, pressure, temperature, as well as to the external magnetic field strength.
New directions: The current focus of spectroscopic research in my lab is on precision measurements of the spectrum of oxygen. We are in the process of measuring absorption strengths for transitions at a wavelength of ~762 nm, with the aim of providing a value for the bandstrength. In the future we will be using a two-photon transition in atomic Rb, with a very precisely measured wavelength, to compare to the transitions in oxygen. The purpose of this experiment is to improve the accuracy with which the oxygen is known so that it can be used as an improved secondary frequency standard for the atmospheric sensing community.
imperfect polarizer effects in magnetic rotation spectroscopy," R.J.
Brecha and L.M.
Pedrotti, Optics Express 5, 101 (1999).
"Non-invasive Magnetometry Based on Magnetic Rotation Spectroscopy of
Oxygen," R.J. Brecha,
Applied Optics 37, 4834 (1998).
rotation spectroscopy of molecular oxygen with a diode laser" R.J.
Brecha, L.M. Pedrotti and D. Krause, J. Opt. Soc. Am. B 14, 1921
(other recent students who have worked on this project are Rob Dollinger and Janet Wendorf )