MULTIDIMENSIONAL FEMTOSECOND SPECTROSCOPIES OF MOLECULAR AGGREGATES AND SEMICONDUCTOR NANOSTRUCTURES - THE NONLINEAR EXCITON EQUATIONS

A unified description of nonlinear optical spectroscopies of molecular aggregates (starting with the Frenkel-Heitler-London Hamiltonian) and semiconductors (starting with the two-band model) is developed using the nonlinear exciton equations (NEE). The equations follow explicitly the complete set of one-, two-, and three-point dynamical exciton var iables relevant for the third-order response. Effects of nuclear motio ns are incorporated through relaxation superoperators calculated pertu rbatively in exciton-phonon coupling. A Green's function expression fo r the third-order response is derived by solving the NEE using a new t runcation scheme based on factorizing the three-point relaxation kerne ls. These results set the stage for designing multidimensional spectro scopies of excitons and analyzing them using coherence-transfer pathwa ys. (C) 1998 American Institute of Physics. [S0021-9606(98)70545-8].