1833 M. Faraday on the basis of the laws of electrolysis hypothesizes the existence of an “electricity atom”.

1869 W. Hittorf studying the electric discharge in gases discovers cathode rays.

1874 G. J. Stoney estimates a value for the elementary charge utilizing a previous value estimated by him for the Avogadro number.

1881 H. Helmholtz rediscovers Faraday’s idea of electricity atom.

1891 G. J. Stoney invents the name “electron” to designate the electricity atom.

1897 J. J. Thomson demostrates that cathodic rays are negatively charged particles and determines the mass/charge ratio; the particle results to be about one thousand times lighter than the hydrogen atom, if one assumes as value for the charge the one measured for ions during electrolysis.

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1899 J. J. Thomson measures the charge of the electron utilizing the discovery, made by his pupil C. T. R. Wilson, that the ions produced ionizing the molecules of the air by means of UV rays act under appropriate conditions as condensation nuclei for water droplets.

1913 R. A. Millikan measures with great precision the charge of the electron substituting the water droplets with oil droplets.

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1923 L. de Broglie Broglie extends the wave-corpuscle dualism introduced by Einstein for the photon, to particles of non zero mass.

1923 C. J. Davisson and C. H. Kunsman observe peaks of anomalous reflection for given incidence angles of low energy electrons on a Platinum crystal.

1924 L. de Broglie discusses his doctoral dissertation in which he develops his theory in detail.

1925 W. Elsasser suggests to interpret the results of the experiments of Davisson e Kunsman on the basis of de Broglie’s theory.

1927 C. J. Davisson and L. H. Germer verify quantitatively de Broglie’s theory by means of the Bragg diffraction operated by low energy electrons impinging on Nickel single crystals

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1928 G. P. Thomson, son of J. J. Thomson, verifies quantitatively de Broglie’s theory by means of the Bragg diffraction operated by high energy electrons on polycrystals of Aluminum and Gold.

1928 E. Rupp observes the diffraction of slow electrons operated by an optical grating using a grazing incidence angle.

1956 G. Möllenstedt and H. Düker observe the interference of electrons utilizing a wire at a certain potential, the electrostatic equivalent of a Fresnel biprism in the optical case, and which causes a split of the electrom beams in two coherent beams.

1957 J. Faget and C. Fert (father of Nobel laureate for physics 2007 A. Fert) observe the interference of electrons both by means of the Fresnel biprism and through two slits in a Young’s type of experiment.

1959 G. Möllenstedt e C. Jönsson perform an experiment similar to what Young did for light and observe the interference of high energy electrons going through three slits 0.6 mm in diameter and separated by 2.2 mm.

1961 C. Jönsson improves the electron optics of the previous experiment and observes the interference of electrons through a number of slits going from 2 to 5, 0.3 mm in diameter and separated by 1 mm.

1949 L. Biberman, N. Sushkin and V. Fabrikant observe the diffraction of electrons effected by an assembly of manganese oxide microcrystals inside an electron microscope, utilizing a beam of very light intensity

1971 K. H. Hermann, D. Krahl, A. Kübler, K. H. Müller and V. Rindfleisch utilize an image intensifier within an electron microscope in order to observe the Fresnel fringes in the images of a slit in a Carbon film and reducing the intensity of the electron beam so as to observe the signals of single electrons.

1976 P. G. Merli, G. F. Missiroli and G. Pozzi utilize an electron microscope equipped with an electronic Möllenstedt & Düker biprism and an image intensifier and observe directly the statistical process of the formation of interference fringes generated by flashes due to single electrons from the impinging electron beam of low intensity.

1989 A group of japanese scientists from Hitachi Ltd. (under the direction of Prof. A. Tonomura) repeats the experiment of interference of single electrons, utilizing a more sophisticated detection system, as allowed by the terrific development of instrumentation occurred during the 13 years gone by since the previous Merli, Missiroli & Pozzi experiment.