Energy transfer among color centers in LiF crystals

In colored LiF crystals there are many absorption and emission bands which cover a wide region of the spectrum from 200 up to 1300 nm without breaking the continuity. In the frame of these favourable conditions we have perfor med some experiments of energy transfer among various color centers. The re sults indicate the existence of efficient exchanges of radiative energy amo ng several bands by using only one exciting wavelength. In particular, the emissions of the F-3(-) and F-2(-) color centers centered at 900 and 1 100 nm, respectively, have been observed by pumping at 672 mn completely outsid e their absorption bands.