High Resolution Electron Microscopy in Organic Chemistry: 1-MEV Electron Microscope in Kyoto

Abstract

Since the epock-making results of 1.5 Å point-to-point resolution obtained with the 500 kV HREM in Kyoto in 1978, we are convinced of the validty of the high voltage electron microscope for the high resolution. However, in order to attain the higher resolution of about 1.3 Å, which is required to resolve a carbon-carbon distance in an aromatic hydrocarbon, there remain so many problems to be solved. In 1990 a new 1 MeV microscope with twin-tank (JE0L-ARM1000) in top-entry type has been installed in Kyoto university aiming to achieve such high resolution.The stability of high voltage is especially important for high resolution because the energy spread of the incident electron beam attenuates the phase transfer function and reduces the image contrast in higher spatial frequencies region. In order to suppress the high voltage fluctuation lower than 1 p. p. m. at 1 MeV and to monitor it, the twin-tank system is adopted, which has produced also satisfactory results in the previous high voltage electron microscopes in Kyoto. Fig. 1 shows the stability of the high tension measured at the top of the accerelating column of the new 1 MeV microscope. The fluctuation is evidently suppressed to less than 1 × 10-6 for five minutes long. The ripple monitored on a sincroscope is also less than 1 p.p.m. The chromatic abberation constant Cc is 3.6mm.