Probing molecular chirality via excitonic nonlinear response

The complete set of fifth-rank tensor components which describe the chirality-induced response of excitons to three femtosecond laser pulses is calculated to first order in the optical wavevector, by including the electric dipole and quadrupole and the magnetic dipole contributions to the induced current. The photon echo signal for the pi-pi* and n-pi* electronic transitions of a helical polypeptides is calculated using the Green's function solution of the nonlinear exciton equations (NEE). Two-dimensional correlation plots of selected tensor components show considerably enhanced crosspeaks with high sensitivity to structural variations.