Electronic spectrum of crystalline lithium fluoride

D. M. Roessler, W. C. Walker


The reflection spectrum of freshly cleaved lithium fluoride has been measured from the near ultraviolet to 28 eV. The real (ε1) and imaginary (ε2) parts of the dielectric response function have been computed via the Kramers-Kronig relations. The Γ exciton band at 12.61 eV (300°K) is asymmetric due to subsidiary structure, but its half-width from a classical dispersion fit is about 0.33 eV with a corresponding oscillator strength of 0.55 per molecule. The band gap is estimated to be 13.60±0.06 eV. A strong peak in the function Im(1ε) near 25 eV is identified as a bulk plasma resonance, and is in agreement with published characteristic electron energy loss work on thin films. © 1967.

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Materials
Curve 1
Temperature K: 300 Wavelength Range, µm: 0.044-0.104 Geometry θ θ' ω': 8° 8° Composition (weight percent), Specifications, and Remarks: Single crystal (2 mm thick); freshly cleaved in air; exposed to a low humidity for about 2 min before transferred to the vacuum; measured in vacuum.
Curve 1
Temperature K: 77 Wavelength Range, µm: 0.105-0.126 Geometry θ θ' ω': 8° 8° Composition (weight percent), Specifications, and Remarks: Single crystal (2 mm thick); freshly cleaved in air; exposed to a low humidity for about 2 min before transferred to the vacuum; measured in vacuum.
Curve 2
Temperature K: 300 Wavelength Range, µm: 0.105-0.137 Geometry θ θ' ω': 8° 8° Composition (weight percent), Specifications, and Remarks: Above specimen and conditions.