Photoconductivity and electron transport parameters in liquid and solid xenon

In photoconductivity excitation spectra of liquid xenon a threshold at 9.20 eV and a dip at 9.45 eV, very near to the peak of the competing $n=1\mathrm{} \left[\Gamma \right(\frac{1}{2}\left)\right]$ exciton transition, were observed. From the results the $\Gamma \left(\frac{3}{2}\right)$ band gap was determined to be $E_G=9.22\mathrm{}\pm 0.01$ eV. This value is very near to the estimate (9.24 eV) based on the density change of xenon on melting. Combining the value for $E_G$ with the measured position of the $n=2\mathrm{} \left[\Gamma \right(\frac{3}{2}\left)\right]$ exciton peak yielded an exciton binding energy $G=1.08\mathrm{}$ eV and effective exciton reduced mass $m^{*}=0.27\mathrm{}$ (in units of electron mass). Using $m^{*}$ and published results of the bulk modulus and mobility, the following parameters were obtained for liquid Xe at 163 °K: relaxation time $\tau =3.4\mathrm{}\times {10}^{-13\mathrm{}}$ sec, mean free path $L=3.3\mathrm{}\times {10}^{-6\mathrm{}}$ cm, absolute value of scattering length $\mathrm{}\left|a\right|=4.2\mathrm{}\times {10}^{-9\mathrm{}}$ cm, absolute value of conduction-band deformation potential $\left|E_{1\mathrm{CB}}\right|=1.0\mathrm{}$ eV. On the other hand, for solid xenon at 161 °K $\tau =8.0\mathrm{}\times {10}^{-13\mathrm{}}$ sec, $L=7.1\mathrm{}\times {10}^{-6\mathrm{}}$ cm, $\mathrm{}\left|a\right|=3.8\mathrm{}\times {10}^{-9\mathrm{}}$ cm, and $\left|E_{1\mathrm{CB}}\right|=0.93\mathrm{}$ eV. The significance of the results is discussed.