The ability to control the environment inside the electron microscope is a very desirable general capability and one long pursued for higher vacuum or chemical reactions (1,2) Here we are primarily concerned with providing the essential facilities for realistic in-situ dynamic studies of chemical reactions between gases or vapors and solids. The compromises with microscope performance have been reduced substantially compared with previous gas experiments (2,3).

The primary applications for the present instrument are to reaction catalysts and the products of reactions where they are solid state materials of commercial value. Firstly, the catalyst may have to be (re)processed after transfer through the air or other hostile (i.e. non-reactor) environment. Secondly, the high vacuum atmosphere in a typical TEM may not be a compatible environment for the catalyst or other material (e.g. if it is solvated). Thirdly, the sequence of events in changes in the microstructure of a chemically active species will likely depend on the atmosphere in which those changes take place or are promoted (e.g. by heating).