New Eu²+ sites in KMgF₃:Eu²+ crystal

The luminescence properties of KMgF(3):Eu(2 + ) are investigated at different pressures in the temperature range 25-292 K. Five new Eu(2 + ) luminescence (NEL) lines due to the [Formula: see text] transition are identified at 362.49 nm (L(1)), 362.53 nm (L(2)), 360.72 nm (L(3)), 360.15 nm (L(4)) and 359.59 nm (L(5)) together with the line at 359.32 nm (L(0)) which is well known in KMgF(3):Eu(2 + ). The emission lines under excitation at 325 nm show a strong dependence on temperature. At 25 K the emission spectrum consists of only two sharp lines, L(1) and L(2). Three additional lines (L(3), L(4) and L(5)) begin to appear with increasing temperature. With a further increase in temperature from 150 to 292 K all the lines disappear except for the single sharp line at 359.32 nm (L(0)). The zero-phonon transition of line L(0) is accompanied by vibronic sidebands. A pressure shift of five NELs is estimated to be about - 0.6 cm( - 1) kbar( - 1) similarly to the shift of line L(0), while the lifetimes of the NELs are about 0.7 ms which is shorter than that (5.2 ms) of L(0) at 80 K. The new luminescence lines are attributed to the Eu(2 + ) ions occupying the K( + ) sites with fluorine vacancy (F( - ) center) complexes.