Polarization modulation infrared linear

Y. Wang, C. Pellerin, C. G. Bazuin, M. Pezolet, Molecular orientation and relaxation in uniaxially stretched segmented ptmo zwitterionomers by polarization modulation infrared linear dichroism. Macromolecules 38(10), 4377-4383 (2005). 

I. Noda, A.E. Dowrey and C. Marcott, Characterization of polymers using polarization-modulation infrared techniques Dynamic infrared linear dichroism (DIRLD) spectroscopy. 

Noda, L Dowrey, A. E. Marcott, C., Characterization of Polymers Using Polarization-Modulation Infrared Techniques Dynamic Infrared Linear Dichroism (DIRLD) Spectroscopy. In Fourier Transform Infrared Characterization of Polymers, Ishida, H., Ed. Plenum Press New York, 1987 pp 33-57. 

When performing polarization-modulation spectrometry, a beam of infrared radiation linearly polarized in the y axis at an angle of 45° to the u axis is incident on the PEM, as shown in Eigure 11.6. This y-polarized radiation can be decomposed into two polarized... 

In the years to follow the key to the measurement of vibrational circular dichroism was the development of photoelastic modulators suitable for work in the infrared spectral region. The first successful measurements of circular dichroism originating from vibrational transitions in the infrared were done by Hsu and Holzwarth (1973) on thin slices of monocrystalline a-NiS04 6 H2O and a-ZnSe04 6 H2O. For this measurements the authors used a normal dispersive IR spectrometer supplemented by a linear polarizer and a photoelastic modulator made from Germanium. 

In an infrared spectrometer equipped with a linear polarizer and a PEM the CD of the sample is then extracted from the detector signal by means of a lock-in amplifier tuned to the operating frequency of the photoelastic modulator. 

In this method, a polarizer and a photoelastic modulator (PEM) are used to switch alternately between two linearly polarized infrared beams, the planes of polarization of which are orthogonal to each other. A PEM used in the mid-infrared region consists of an infrared-transparent isotropic crystal (usually ZnSe) and a quartz oscillator. The latter is used to make the ZnSe crystal anisotropic by applying pressure to the ZnSe crystal in one direction (called here the u axis), the anisotropic crystal shows different refractive indices in different planes of polarization. 

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