Transit-time measurements of electron mobility in AgCl have been extended to very low temperatures. Results are presented for an air-grown Bridgman crystal and for a Kyropoulos crystal of high purity. A maximum mobility of about 250 ${\mathrm{cm}}^2$/volt-sec at 80°K was found for the former and a maximum of 480 ${\mathrm{cm}}^2$/volt-sec at 55°K for the latter. It appears that imperfections strongly influence the mobility at low temperatures. At intermediate temperatures the data are in best agreement with the theory of interaction with optical modes of vibration of the lattice from which it is found that ${\mu }_0=30(e^{\frac{280}{\tau }}-1)$ ${\mathrm{cm}}^2$/volt-sec. This corresponds to a polaron effective mass of $\frac{m^{*}}{m_e}=0.28\mathrm{}$ where $m_e$ is the free electron mass.

• Received 8 July 1957

DOI:https://doi.org/10.1103/PhysRev.108.281