ANTIRESONANCE PHENOMENA IN ABSORPTION SPECTRA OF RARE-EARTH IONS IN X-IRRADIATED CAF2

Some absorption lines of rare-earth ions in calcium fluoride were found to be considerably affected by irradiation with x rays. These narrow lines, which appeared superimposed on a broad background of color-center absorption, were in some cases over 100 times stronger after irradiation and had strongly asymmetric line shapes, often resulting in an antiresonance dip. It is proposed that these effects are caused by interaction of the rare-earth ion and a neighboring color center. © 1969 The American Physical Society.