Improved Optical Spectroscopy Technique - Graphite Defects Observed by Electron Microscopy - Principles of Self-Modulating Derivative Optical Spectroscopy - Ricerche di fisica dei solidi presso il Laboratorio di Microscopia Elettronica dell'IEN

摘要

There are several spectroscopic problems for which the status of the present technique is still unsatisfactory. Outstanding among these problems is solid state optical absorption spectroscopy, where poor quality information is currently ob¬tained and substantial improvements are badly needed. On the other hand, the great achievements rendered possible in microwave spectroscopy by the use of phase sensitive detectors (such as "lock-in" amplifiers) are well known. Such electronic de¬vices allow in fact the detection of signals as weak as two orders of magnitude below the level of back¬ground noise.nStructural defects of natural graphite are characterized by Newton-ring-like electron microscopic con¬trast. Pictures arc given, evidencing their aspect, their peculiar distribution (often corresponding to linear alignment), and their behavior at high temperatures. A discussion is presented concerning related theoretical and experimental results of other authors and in particular the relationship of these defects to radiation damage.nThin paper presents the theoretical principles underlying a new technical of optical spectroscopy, characterized by the fact that the record of a spectrum, differentiated and efficiently purified of noise, is obtained ill a direct, and wimple way. The interest of derivative optical speeds copy in evidenced by calculations showing for a typical case the gain to be expected. A set of equations is then given showing the dependence of the new spectrometer performance on the principal design parameters. Experimental results will he reported in another paper.