Light microscopy photomultiplier

Figure 4.3 Signal collection by the Everhart-Thornley detector. B, backscattered electron trajectory SE, secondary electron trajectory F, Faraday cage S, scintillator LG, light guide PM, photomultiplier tube. (Reproduced with kind permission of Springer Science and Business Media from J.I. Goldstein et al, Scanning Electron Microscopy and X-ray Microanalysis, 2nd ed., Plenum Press, New York. 1992 Springer Science.)...

N+I biphase. The nematic-isotropic intervals as observed by microscopy provide a very inadequate representative of the extent of the N+I biphase. This is clearly illustrated on Fig. 1, where the [T2 Tc interval measured by microscopy is considerably smaller than the biphase observed by NMR. Microscopic observation under slow rates of scanning with measurement of the transmitted light intensity by means of a photomultiplier, to eliminate observer subjectivity, gives substantially the same results. Fig. 1 shows that the N+I biphase extends well into what is seemingly a "homogeneous nematic phase. In polymer DDA-9, for example, the shortest chains become isotropic approximately 90 before chains whose mass is Mn> 10,000 and act as isotropic "contaminants of the polydisperse mesophase. 

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