SPECIAL >IETIIODS 



8. KuMAi, M., "Electron-microscope study of 



snow-crystal nucli II." Geofisica pura e 

 applicata-Milano, 36, 169-181 (1957). 



9. KuRoiWA, D., "Electron-microscope study of 



atmospheric nuclei." T. Hori (ed.) "Studies 

 on fog," Sapporo, pp. 349-382 (1953). 



10. Lodge, J. P., "Analysis of micron-sized par- 



ticles." Anal. Chem., 26, 1829-1831 (1954). 



11. Maruyama, H., "Electron-microscope study 



of the ice crystal nviclei." Meterology and 

 Geophysics, Tokyo, 7, 251-266 (1956). 



12. MUGURUMA, J. AND HiGUCHI, K., "On the 



etch pits of snow crystals," /. Meteor. Soci. 

 of Japan. Ser. II. 37, 71-75 (1959). 



13. Nakaya, U., "The formation of ice crystals." 



Compendium of Meterologj^, American 

 Metero. Soc, pp. 207-220 (1951). 



14. Nakaya, U., "Surface nature of ice crystals," 



in "Artificial Stimulation of rain," H. 

 Weickman (ed.) Pergamon Press, New York, 

 pp. 386-389, 1955. 



15. Nakaya, U. and Kumai, M., "Electron- 



microscope study of center nuclei of snow 

 crj^stals III. J. Meteor. Soci. Japan, 75th 

 anniversary volume, pp. 49-51, 1957. 



16. Ogiwara, S. and Okita, T., "Electron- 



microscope study of cloud and fog nuclei," 

 Tellus, 4, pp. 233-240 (1952). 



17. Schaefer, V. J., "The formation of ice crys- 



tals in the laboratory and the atmosphere," 

 Chem. Rev. 44, 291-320 (1949). 



18. Schaefer, V. J., and Harker, D., "Surface 



replicas for use in the electron microscope," 

 /. Applied Phys. 13, 427-433 (1942). 



19. Schaefer, V. J., "The question of meteoritic 



dust in the atmosphere," in "Artificial 

 stimulation of rain," H. Weickman (ed.) 

 Pergamon Press, New York, pp. 18-23, 1955. 



20. VoNNEGUT, B., "Nucleation of ice formation 



by Agl particles." Final Rep. No. RG 140, 

 Gen. Elec. Res. Labs., pp. 26-34, 1948. 



21. Yamamoto, G. and Ohtake, T., "Electron 



microscope study of cloud and fog nuclei," 

 Science Report. Tohoku Univ. Ser. 5 Geo- 

 phys., 5, 141-159, 1953. 



MoTOi Kumai 



SPECIAL METHODS 



One of the aims of electron microscopy is 

 to observ'e the arrangement of constituent 

 atoms and molecules of materials. Recent 

 improvement in the electron microscope has 

 made it possible to observe the lattice image 



of crystals of which spacing is less than 10 A. 

 Miiller, using the field emission type elec- 

 tron microscope, has succeeded in observhig 

 directly the arrangement of atoms such as 

 W, Re, etc. Besides the problem of high reso- 

 lution, various special methods for electron 

 microscopic observation have been tried to 

 develop the fields of its application. In this 

 chapter some of these special methods, which 

 have been studied mainly in Japan, arc in- 

 troduced and their constructions, perform- 

 ances and experimental results are briefly 

 described. They are as follows: 



(1) Reflection method 



(2) Specimen cooling method 



(3) Specimen heating method 



(4) Gas reaction method 



Reflection Method 



In obser\dng solid surfaces by the trans- 

 mission electron microscope, we usually use 

 the replica film which is reprinted from the 

 surface structure of the solid. Then, a method 

 for direct observation of solid surfaces is 

 naturally desired, just as for an optical mi- 

 croscope for metallurgy. There are two meth- 

 ods in the deflecting mechanism of the elec- 

 tron beam in a reflection microscope: (1) 

 makes the electron beam strike the specimen 

 by mechanically inclining the electron gun 

 and condenser lens at any desired angle ; the 

 other (2, 3) makes the electron beam strike 

 the specimen by using two pairs of deflecting 

 coils without inclination of the illuminating 

 system. This article describes the latter. 



Construction of Reflection Electron 

 Microscope. Fig. 1 shows the principle of 

 the reflection device for JE]\I-5Y universal 

 electron microscope and Fig. 2 the specimen 

 chamber equipped with this device. For 

 changing the incident angle /3, two pairs 

 of deflecting coils are inserted between the 

 condenser lens and the specimen chamber as 

 shown in Fig. 1. The electrons emitted from 

 the electron gun are deflected from the optical 

 axis by the upper pair and again to the speci- 

 men by the lower pair. It is possible to 



259 



