Chemistry and Biochemistry Faculty Works

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Browsing Chemistry and Biochemistry Faculty Works by Author "Dam, R. J."

Now showing 1 - 4 of 4
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    Photoelectron microscopy and quantum yields of membrane phospholipids
    (Proceedings of the Electron Microscopy Society of America, 1976) Griffith, O. H.; Dam, R. J.
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    Photoelectron microscopy of biological surfaces. Excitation source brightness requirements
    (Society of Photo-Optical Instrumentation Engineers, 1976) Dam, R. J.; Griffith, O. H.
    Photoelectron microscopy is a surface technique which provides topographical infor mation using the photoelectric effect as a basis for contrast. Progress in the biolo gical applications of this technique is briefly reviewed. Due to relatively low quantum yields, photoemission from biological samples is weak and an image intensifier is used in order to visualize and record the photoelectron image. Currently the limiting magnification is determined by UV power incident on the sample. Power requirements for high-magnification imaging are calculated in terms of microscope, sample, and image intensifier parameters. To approach 40 A resolution, an instrument magnification of 12,000-50,000 is required along with a UV intensity of 0.01 to 10 Watts/cm2 depending on the wavelength and sample. For a tightly focused laser source the total power re quirement is 1 mWatt or less.
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    Photoelectron microscopy of biomembranes: Observation of external photomission from spinach chloroplasts
    (Annual Proceedings of the Electron Microscopy Society of America, 1975) Dam, R. J.; Lesch, G. H.; Deamer, D. W.; Griffith, O. H.
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    Photoelectron microscopy of organic surfaces: The effect of substrate reflectivity
    (Journal of Applied Physics, 1976-03) Dam, R. J.; Griffith, O. H.; Rempfer, G. F.
    Photoelectron measurements of thin organic films deposited on a metal substrate may contain information from deep within the sample, derived from reflected ultraviolet light. This effect depends on the reflectivity of the substrate, the sample thickness and optical absorption coefficient, and the photoelectron escape depth. Calculations are given for phthalocyanine as a specific example. Contrast reversal and apparent seethrough effects resulting from reflection are predicted in overlapping thin films. Photoelectron micrographs of thin films and grid patterns of phthalocyanine show that the reflection model is essentially correct. This effect can be substantially reduced by using a nitrocellulose-coated carbon substrate.