Probing spatial correlations in a system of polarizable nanoparticles via measuring its optical extinction spectrum

It is shown that quantitative information on spatial correlations in a system of polarizable particles can be extracted directly from its experimentally measurable optical spectra. For a collection of metallic nanoparticles (NPs), it is demonstrated that the degree of shortrange correlation in NP’s positions can be evaluated by an appropriate numerical analysis of the extinction spectrum in the surface plasmon resonance region, given the polarizability of an individual NP. The spectrum analysis consists in the evaluation of a single number, which is the derivative of the ensemble response function in the vanishing polarizability limit, using the Tikhonov regularization method. This number has to be compared to pre-calculated values for a model NP system with given density and correlation parameters.Financial support from the Portuguese Foundation for Science and Technology (FCT) through Projects PTDC-FIS-113199-2009. PEst-C/FIS/UI0607/2011 and PEst-C/MAT/UI0013/2011 is gratefully acknowledged