SPECTROSCOPIC PROPERTIES OF CS2ZNCL4-CO2+

The absorption and luminescence spectra of a Cs2ZnCl4 single crystal d oped with Co2+ ions are reported. Two strong, broad peaks in the absor ption spectra are assigned to (4)A(2) --> T-4(1)(F) and (4)A(2) --> T- 4(1)(P) transitions, respectively. Other bands belong to transitions f rom ground level (4)A(2) to levels arising from split (2)G, H-2, P-2, D-2, F-2 terms. The absorption spectra were dependent on polarisation. The crystal field parameter Dq and the Racah parameters were calculat ed as Dq = - 325 cm(-1), B = 728 cm(-1) C = 3349 cm(-1). The spin-orbi t coupling constant lambda was found equal to 162 cm(-1). A broad emis sion band centred at 11 800 cm(-1) was assigned to T-4(1)(P) --> (4)A( 2)(F) transition. Decay curves of the observed emission were non-expon ential, its short decay time, about 50 ns, indicating the electric dip ole character of the observed emission and the strong influence of non -radiative processes. (C) 1997 Elsevier Science B.V.