抄録
Reflection spectra of electron waves from a cleaved surface of NaCl and from the surface covered with condensed crystallits of the crystal were taken simultaneously on the same photographie plate with a view to obtaining accurate values for ratio between the wave length and the spacing. The apparent inner potential is deduced from the former spectra for each order reflection Though the inner potential, evaluated by using Uyela's formula from high order reflections has a definite value, the value derived from the first and the second order reflections still show remarkable deviation from the definite one. An interpretation of the second order reflection led us to a conclusion that an expansion of the spacing of the surface layers is contrary to the contraction deduced from the theoretical ground by Lennard-Jones and others Other possibilities for the explanation of the low order reflections are also discussed
