Polarization-modulation spectrometry

Polarization-Modulation Spectrometry and its Application to Reflection-Absorption Measurements... 

In this chapter, a sensitive method for measurement by continuous-scan Fourier-transform infrared (FT-IR) spectrometry called polarization-modulation spectrometry is introduced this is a useful method for measuring, with high signal-to-noise ratio, not only the reflection-absorption spectra of thin films adsorbed onto metal substrates but also other spectra such as vibrational circular dichroism (VCD) spectra. Polarization-modulation spectrometry is a type of double-modulation FT-IR spectrometry [1], In this chapter, descriptions of double-modulation spectrometry are given first, then polarization-modulation spectrometry is discussed, and then its application to the measurement of reflection-absorption spectra of thin films on metal substrates is discussed. 

In this section, polarization-modulation reflection-absorption spectrometry, a representative application of double-modulation spectrometry, is described. When polarization-modulation spectrometry is applied to reflection-absorption measurements for thin Aims on metal substrates, the polarization of the infrared beam incident on a thin film is alternately switched between being parallel and perpendicular to the plane of incidence, and... 

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 a similar manner to that developed with Equations (11.1a) and (11.1 b) for the intensity of the beam of infrared radiation that has passed through the target and reference samples in double-modulation spectrometry, when polarization-modulation spectrometry is applied to a reflection-absorption measurement of a thin film adsorbed onto a metal substrate, the intensity of reflection B (v, f) is expressed in the following form as a function of wavenumber V and time f. 

As described above, also in polarization-modulation spectrometry, Bjc(v) and are first measured, and then their ratio B v)/B v) is used to determine AAj(v). These procedures are schematically illustrated in Figure 11.8, in which all the data are depicted in spectral forms. 

Measurement of the Reflection-Absorption Spectra of Thin Films on Metal Surfaces by Polarization-Modulation Spectrometry... 

Bjc(v) and B v) can be determined by the same procedures as described for doublemodulation spectrometry. However, as isclear from a comparison of Equations (11.1b) and (11.15a), polarization-modulation spectroscopy must use 2/ j as the synchronizing signal for the lock-in amplifier. By using B v) and B v) obtained as described above, the difference between A//(v) and Aj (v) is determined. The second term of Bdc(v) is negligibly... 

EDXRF (energy dispersive x-ray fluorescence) spectrometry works without a ciystal. An EDXRF spectrometer includes special electronics and software modules to take care that all radiation is properly analyzed in the detector. It provides a lower cost alternative for applications where less precision is required. The high-end uses the 3D EDXRF techniques featuring a 3-dimensional, polarizing optical geometry. 

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