EXPERIMENTAL OBSERVATIONS OF ABSORPTION INFRA-RED EMISSION AND EXCITATION SPECTRA OF CR3+ IONS IN ZNWO4

Optical absorption, infra‐red emission, and excitation spectra have been measured for trivalent chromium ions in the zinc tungstate lattice. In contrast to the case of ruby the lowest excited state is 4T2(F) and emission results from the 4T2−4A2 transition. The emission at about 1 μm is of broad band type with a decay time of about 10−5 s and involves a significant Stokes shift. These characteristics are consistent with the strong dependence of the energy of the 4T2 state on the crystal field parameter, and a large activator‐lattice interaction. Rhombic symmetry is indicated for the Cr3+ ion site, but tetragonal distortion occurs for the excited states. Copyright © 1968 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim