Transient optically detected ESR in the excited state of ruby

The dynamics of the(²E) state of Cr³⁺ in Al₂O₃ have been investigated. After excitation by a short laser pulse (<10ns) the relative intensity of the optically detected ESR signal (ODMR) as a function of the delay timet_d after the excitation is measured. A remarkable increase was found upon lengtheningt_d, while the line width remained constant. This increasing population difference of the Zeeman levels of(²E) can be explained by different resonant-reabsorption induced effective lifetimes. The experimental data could be reproduced by use of a phenomenological model.