Time-resolved profiles in modulated polarization spectroscopy

The absorption of a modulated light beam in which the state of the polariza tion is continuously variable is discussed. It is now possible to measure t he average time-dependent profile for the polarization cycle of such a beam , and corresponding theoretical descriptions are needed in order to extract the information contained in it. This work generates such a description. B ased on a semiclassical treatment of light/matter interactions, a three-par ameter fit function is derived that permits the simultaneous extraction of absorbance, linear dichroism, and circular dischroism from the profile for various types of uniformly oriented, partially oriented, and isotropic mate rials and combinations of them. The theoretical expressions are used to ana lyze data for (+)-3-methylcyclopentanone, the results being (1) an increase of the S/N ratio, (2) the simultaneous generation of absorption and dichro ism spectra of identical quality, and (3) a description of window adsorbate s of the cyclopentanone material. The Jones parameters for the macroscopic description of polarized light interactions with matter are reformulated at the microscopic (i.e., transition moment) level, and an alternative deriva tion of the Jones matrix is given.