Pressure of correlated layer-charge and counterion fluctuations in chargedthin films

We predict the fluctuation contribution to the interaction between two surf aces with both mobile layer charges and delocalized counterions. The correl ation (coupling) between the layer-charge fluctuations and the counterion f luctuations (around a piecewise homogeneous mean-field density profile) is taken into account in the Gaussian approximation. We find that this correla tion significantly increases the magnitude of the: interlayer fluctuation a ttraction. The counterion fluctuation pressure is calculated as a function of the intersurface distance and we show how the large and small distance l imits correspond to three-dimensional (3D) and 2D fluctuations, respectivel y. In addition, we predict the charge density-density correlation functions . Experimental implications of the model are discussed. [S1063-651X(99)1391 1-4].