Observation of intrinsically localized modes in a discrete low-dimensionalmaterial

We report the experimental observation of intrinsic dynamically localized v ibrational states in crystals of the highly nonlinear halide-bridged mixed- valence transition metal complex {[Pt(en)(2)] [Pt(en)(2)Cl-2] (ClO4)(4)}, w here en = ethylenediamine. These states are identified by the distinctive s tructure and strong redshifts they impose upon the overtone resonance Raman spectra. Quantitative modeling of the observed redshifts is presented base d on a nonadiabatic coupled electron-lattice model that self-consistently p redicts strong nonlinearity and highly localized multiquanta bound states. [S0031-9007(99)08915-2].