Time-Resolved Profiles in Modulated Polarization Spectroscopy
The absorption of a modulated light beam in which the state of the polarization is continuously variable is discussed. It is now possible to measure the 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. Based on a semiclassical treatment of light/matter interactions, a three-parameter 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 materials and combinations of them. The theoretical expressions are used to analyze data for (+)-3-methylcyclopentanone, the results being (1) an increase of the S/N ratio, (2) the simultaneous generation of absorption and dichroism spectra of identical quality, and (3) a description of window adsorbates of the cyclopentanone material. The Jones p...
The Selective Digital Integrator: A New Device for Modulated Polarization Spectroscopy.
A new device, a selective digital integrator (SDI), for the acquisition o f modulated polarizaticm spectroscopy (MPS) signals is described. Special attention is given to the accurate measurement o f very small (AC component o f interest < lO'"’ x DC component), rapidly modulated (-50 kH z) signals at or below noise levels. Various data acquisition methcxis and problems associated with the collection o f modulated signals are discussed. The SDI solves most o f these problems and has the following advantages; it provides the average-time resolved profile o f a modulated signal; it eliminates errors if the modulation is not sinusoidal; it enables sqiarate m easurem aits o f the various phases o f the signal modulation cycle; it permits simultaneous measurement o f absorption, circular dichroism (CD) and linear dichroism (LD) spectra; it facilitates 3-D absorbance measuremraits; it has a wide gain-switching-free dynamic range (10 orders o f magnitude or more); it offers a constant S/N ratio mode o f operation; it eliminates the need for photomultiplier voltage feedback, and it has faster scanning speeds. The time-resolution, selectivity, wide dynamic range, and low-overhead on-the-fly data processing are useful for o ther modulated spectroscopy (MS) and non-MS experiments such as pulse height distribution and time-resolved pulse counting measurements. The advantages o f the MPS-SDI method are tested on the first Rydberg electronic transitions o f (+)-3-methylcyclopentanone. The experimental results validate the predicted SDI capabilities. However, they also point to two difficulties that had not been noted previously: the presence o f LD in a gaseous sample and a pressure-depaidence o f the relative peak heights o f the CD spectrum. Models for these anomaUes are proposed. The presence o f the oscillatory LD (but not an LD background) is explained with a sample cell model based on the observed polarization-depoidœt time-resolved profiles o f transmitted light intaisity. To obtain expressions for these intensities, a theoretical background, which provides a new approach to xvi R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. the treatment o f light/matter interaction, is included as an Appaidix. To explain the second anomaly, present only at high optical daisities, a model based on the presoice o f scattered light is introduced and verified. The mode o f correction for the scattering problem is outlined.
Substation automation based on IEC 61850 with new process-close technologies
New technologies in primary equipment like nonconventional instrument transformers require new interfaces to the substation automation system. The future standard IEC 61850 perfectly supports this requirement. With the introduction of the new technologies and the use of IEC 61850, a more decentralized architecture of the substation automation system will be possible. This provides several benefits but a careful system design is required to maintain the overall reliability of the system.