<title>Photoelectron Microscopy Of Biological Surfaces Excitation Source Brightness Requirements</title>

Abstract

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.

Photoelectron microscopy of cell surfaces

“…Photoelectron micrographs have been previously reported for sectioned biological samples (Griffith et al, 1972;Engel & Grund, 1974), brain cell nuclei (Grund et al, 1975), chloroplasts (Dam et al, 1975a) and homogeneous preparations of hemes (Dam et al, 1974a) and chlorophyll (Dam et al, 1975b). The specimens examined here are unstained, uncoated chick embryo fibroblasts.…”