The transient volume change of $\alpha$-quartz and fused silica induced by irradiation with an electron pulse has been measured above 80 K. It is shown that transient changes of volume and optical absorption due to the ${E_1}^{\prime }$ centers (oxygen vacancies) decay in parallel and that the volume change per ${E_1}^{\prime }$ center is of the order of a unit molecular volume. The results show unambiguously that recombination-induced defect formation occurs in Si${\mathrm{O}}_2$ but the defects created are not stable even at low temperatures.

• Received 18 April 1983

DOI:https://doi.org/10.1103/PhysRevLett.51.423