Theory of magnetic linearly polarized emission. I. Paramagnetic molecules in a rigid isotropic medium

摘要

A formal theoretical treatment of magnetic linearly polarized emission (MLPE) is developed for luminescent molecular systems. In the MLPE experiment, a constant magnetic field is applied to a luminescent sample and the emission is detected along a direction orthogonal to the direction of the applied field. The emission is analyzed for its linear polarization parallel (par;) and perpendicular (perp;) to the direction of the applied magnetic field, and the principal MLPE observable is Dgr;I=Ipar;minus;Iperp;(whereIdenotes emission intensity). Excitation may be accomplished along any direction and it may be polarized or unpolarized. Explicit theoretical consideration is given to the MLPE spectra of molecular systems possessing either a paramagnetic emitting state or a paramagnetic ground state. The influence of excitation photoselection processes, excitationndash;emission experimental geometries, magnetic field strengths, and temperature on the MLPE spectra of such systems is examined for the case in which the molecules are embedded in a rigid, isotropic medium (such as a solid matrix or glass). MLPE spectra are calculated for a number of model systems as a function of various experimental and molecular parameters. Relationships between MLPE observables and molecular spectroscopic and structural properties are discussed.