Optical Constants of Solid Xenon in the Vacuum-uv Region

The reflectance spectrum in the range 1180–1600 Å solid xenon was measured near 4°K. The Kramers–Kronig inversion technique was used to evaluate the real part $\mathrm{\epsilon \prime }$ and the imaginary part $\mathrm{\epsilon ″}$ of the dielectric constant. A new self‐consistent approximation method was developed and used to evaluate the contribution of absorption bands lying beyond the range of measurements to the phase of the reflection. The $\mathrm{\epsilon ″}$ vs photon energy $E$ curve thus obtained exhibited all the details of the best thin‐film absorption measurements, and it also showed two hitherto unknown peaks, at 8.76 and 8.93 eV, respectively. Resolution of the $\mathrm{\epsilon ″}$ vs $E$ curve into a sum of absorption bands was an inherent part of the new approximation method. From this resolution, the oscillator strengths $f$ of the transitions were determined. The largest $f$ value, namely 0.16, was found for the lowest‐energy peak at 8.378 eV, as compared with $\text{f\hspace{0.17em}=\hspace{0.17em}0.256}$ for the corresponding ${}^3{P}_1$ resonance line in xenon gas. The $f$ value for this band was also computed on the basis of simple theory, whereby the ground state was approximated by a Slater function and the excited state by the Wannier function derived from free‐electron Bloch functions. The result thus calculated was in good agreement with the measured oscillator strength, assuming resonable values for the average dielectric constant. The conclusions of the present work are thus consistent with predictions of the intermediate exciton model.