title: Rotational angular momentum polarization: the influence of stray magnetic fields.
abstract: We show that weak residual magnetic fields can significantly affect the preparation and measurement of molecular rotational angular momentum alignment in a typical gas-phase stereodynamics apparatus. Specifically, polarization spectroscopy, a third-order nonlinear spectroscopic technique, is used to prepare and probe the collisional and noncollisional losses of rotational angular momentum alignment of OH X (2)Pi. Residual magnetic fields of the order of the geomagnetic field are shown to have a significant effect on the prepared polarization on a submicrosecond timescale. This can be expected to be a significant effect for many gas-phase free radicals, such as those of interest in combustion, atmospheric chemistry, and the burgeoning field of cold molecules. We demonstrate a simple experimental remedy for this problem.
authors.affiliation: School of Engineering and Physical Sciences, William H. Perkin Building, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom.
authors.forename: Sarantos
authors.initials: S
authors.lastname: Marinakis
authors.forename: Grant
authors.initials: G
authors.lastname: Paterson
authors.forename: Graham
authors.initials: G
authors.lastname: Richmond
authors.forename: Michael
authors.initials: M
authors.lastname: Rockingham
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Costen
authors.forename: Kenneth G
authors.initials: KG
authors.lastname: McKendrick