Basic Electron Microscopy
Arthur Rowe
The Knowledge Base at a Simple Level
Introduction
 These
3 presentations cover the
fundamental theory of electron microscopy
 In presentation #1 we cover:
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the bits of optics we need to know
production of an electron beam
why we need vacuum & how we get it
the foundations of electron optics
Sites for Electron Microscopy
These sites contain useful information concerning most of the range of techniques
available
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Microscopy & Imaging: Resources on the WWW (University of Arizona)
http://www.pharm.Arizona.edu/centers/tox_center/swehsc/exp_path/mi_onw3.html
Everything in sight (site ?), including the “Electron Microscopy Yellow Pages” !
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Gina Sosinsky’s EM Outreach program:
http://em-outreach.sdsc.edu/
Based at the Supercomputing Center at San Diego, this site
includes a very full set of Web-based lecture notes. Good text, but
sadly, Gina has had problems getting many microscopists to agree
to copyright release for their work, so for the moment the
illustrations are rather minimal. One slight mis-statement, it is said
that shadowing usually gives much worse resolution than negative
staining. Not true.
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Analytical Imaging Facility at Albert Einstein College of
Medicine:
http://www.aecom.yu.edu/aif/welcome.htm
Concentrates heavily - as you would expect - on the analytical
side of microscopy. All types are considered, light and electron
microscopy being integrated together. As you might expect from
the Albert Einstein, this site is a fantastic resource
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Helen Saibil’s home page:
http://www.cryst.bbk.ac.uk/~ubcg16z/saibil.htm
Lovely images and some movies of selected protein-based
systems, including chaperonin (GroEL - GroES) and pore-forming
toxin (pneumolysin)
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UNSW’s Image Gallery:
http://srv.emunit.unsw.edu.au/html/gallery/gallery.htm
Slanted towards histology in the biology section, but good images
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University of Sussex - EM site
http://www.biols.susx.ac.uk/Home/Julian_Thorpe/cover.htm
some good teaching material at a simple level, as well as some
pretty images.
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and you can of course go on
almost for ever, if you enter
‘electron microscopy’ into a
search engine (SCIRUS is
good for science)
so now, on to the basics . . . . . .
imaging with a simple lens
the meaning of focal length
when we image a simple point
definition of resolution
the electron gun
wavelength & voltage
why high vacuum ?
• mean free path of electrons v short in air
- at least 10
-5 mbar
usually aimed for
• also
- tungsten filaments burn out in air
- columns must be kept dust free
• achieved by 2-fold pumping:
rotary (mechanical) pump + diffusion pump
or + turbo pump
how does a diffusion pump work?
the electromagnetic lens
the electromagnetic lens
the transmission electron
microscope
The TEM Column
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Gun emits electrons
Electric field accelerates
Magnetic (and electric) field control
path of electrons
Electron wavelength @ 200KeV 
2x10-12 m
Resolution normally achievable @
200KeV  2 x 10-10 m  2Å