A search for infrared absorption by self-trapped excitons in sodium chloride

Reports experiments to detect transient infrared absorption in the spectral range 0.1 to 2 eV following electron pulse excitation of NaCl. Specifically, a transition of the triplet self-trapped exciton predicted by theory to occur in the 0.7-1.1 eV range was sought. The experiment demonstrates the absence of any such transition, with sensitivity limits corresponding to 2% of the predicted oscillator strength. Assignment of features in the visible absorption spectra of self-trapped excitons is discussed in light of this result.