Fermi radii of lithium by positron annihilation.

• Main Author: Paciga, John Joseph
• Language: English
• Published: University of British Columbia 2011
• Subjects: Fermi surfaces; Lithium
• Online Access: http://hdl.handle.net/2429/33892

A positron annihilation experiment involving collinear point geometry is used to make a direct comparison of the k₁₁₀ and k₁₀₀ Fermi radii in a single crystal of lithium. It is found that is k₁₁₀ greater than k₁₀₀ by 5.6 ± 1.2%, in agreement with theory and a phenomenological interpretation of an earlier long slit experiment. The higher momentum components of the positron wavefunction are calculated by a direct method and found to be negligible. On the other hand, a less straightforward estimate based on a flattened Seitz potential shows that the higher momentum components of the electron wavefunction significantly reduce the experimentally observed anisotropy. Hence, the difference of 5.6% should be regarded as an upper limit on the true distortion of the Fermi surface of lithium. === Science, Faculty of === Physics and Astronomy, Department of === Graduate