We utilize the optical transitions of Yb$^{ 2+}$ excited by an ultraviolet optical parametric amplifier to probe electron trap liberation in MgF$_{ 2}$ via the observation of a photoluminescence enhancement effect induced by a subsequent infrared pulse from a free-electron laser. The temperature dependence of the enhancement suggests that we liberate very shallow traps having a depth of approximately 17 cm$^{ -1}$. The observed `trap spectrum' is consistent with a simple model of a Coulomb trap.
Categories: cond-mat.mtrl-sci physics.chem-ph