The Pb2+(Li) and Pb2+(Na) centres in KCl crystals

Emission, absorption and magnetic circular dichroism spectra have been stud ied on Li+- and Pb2+-codoped KCl crystals. Two emission bands (one is the A (T)-like emission and the other the A(X)-like emission) have been observed at 350 and 453 nm at room temperature, respectively These emissions have be en observed by excitation in the absorption bands with peaks at 270 and 281 nm. These emission bands are attributed to the Pb2+(Li) centre, where a Pb 2+ ion has a Li+ ion at one of the six nearest neighbouring cation sites. M easurements have been also made on Na+- and Pb2+-codopcd KCl crystals. Unli ke the Pb2+(Li) centre, only the A(T)-like emission band with a peak at 347 nm due to the Pb2+(Na) centre has been observed. It is suggested that such a difference is due to a difference in the position of the impurity alkali ion substituted for the K+ ion.