Nuclear Scattering of High Velocity Electrons. Part I: Nuclear Scattering of High Velocity Electrons. Part II: Reflection of Electrons from Solid Surfaces

Citation

Neher, Henry Victor (1931) Nuclear Scattering of High Velocity Electrons. Part I: Nuclear Scattering of High Velocity Electrons. Part II: Reflection of Electrons from Solid Surfaces. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/3DBK-P233. https://resolver.caltech.edu/CaltechETD:etd-05132003-124602

Abstract

Part I.

The results reported in this thesis may be summarized as follows:

1. Nuclear scattering by thin foils has been extended from 80,000 to 145,000 volts.
2. A more critical criterion for single scattering by thin foils is obtained which depends on the shape of the curve connecting ρ, the amount of scattering, with the angle.
3. Secondary electrons are eliminated by applying high equivalent stopping potentials.
4. Dependence of scattering on energy of primary beam is found to agree well with either Mott's equation or with the relation k/V², but is at variance with the classical relativistic theory.
5. Comparison of values of scattering for Al, Ag and Au shows thatρ increases faster than Z².
6. Scattering is obtained as a function of angle from 95° to 173°. For Al the dependence found experimentally agrees well with either Mott's or Rutherford's equation. The latter also gives the correct dependence on angle for Ag and Au. Mott's equation is not applicable for these heavy elements.
7. Experimental absolute values for scattering for Al compared with theory give ρ = 1.32 of the value given by Mott's equation. This relation is valid within the ranges θ = 95° -173°, V = 56-145 KV.
8. Secondary electrons coming from the foil are distributed according to the simple cosine law.
9. No evidence of loss of energy due to radiation is found.

Part II.

The main results obtained in Part II of this thesis may be summarized as follows:

1. Values of the reflection coefficient, ρ₀, for Be, c, Al, Cu, Brass, Sn and Pb are obtained from 45 to 128 KV.
2. A decrease of ρ₀ with increase of voltage is found which is most pronounced for the light elements.
3. The angular distribution of emitted electrons is given very accurately by Lambert's cosine law of radiation.
4. Absorbed gases cause the surface to emit many slow electrons which is most noticeable for the light elements. This fact probably accounts for the larger values reported by some observers.
5. With Be, C, and Al, a change with time of the number of slow electrons emitted was found upon going from high to low voltages.

Thesis Files