LARGE NONLINEAR-OPTICAL EFFECTS AND SMALL LINEAR ABSORPTION OF INORGANIC CLUSTERS (ME(4)N)(2)[CU-4(SPH)(6)] AND (ME(4)N)(2)[AG-6(SPH)(8)]

Nonlinear optical (NLO) properties of the clusters (Me(4)N)(2)[Cu-4(SP h)(6)] (I) and (Me(4)N)(2)[Ag-6(SPh)(8)] (II) were studied with a 7 ns pulsed laser at 532 nm. Both I and II exhibit NLO absorption and NLO refraction, which can be roughly described by third-order processes. A wide transparent window (lambda = 400-1000 nm) was observed for both clusters, which leads to relatively large values of the figure of meri t, W (=\n(2)I/(alpha(o) lambda 2)\). The W value is 32 and 5 for I and II, respectively, at incident irradiance of 0.3 GW cm(-2). The nonlin ear optical properties of the clusters were related to the extent of e lectron delocalization of their HOMOs and LUMOs. Structural factors th at may lead to optimization of linear and nonlinear optical performanc e of a material were discussed.