Vibrational-exciton relaxation probed by three-pulse echoes in polypeptides

Infrared photon echoes are simulated for an anharmonic vibrational dimer re presenting a dipeptide in the amide I spectral region by solving the nonlin ear exciton equations for the vibrational-exciton model. New relaxation-ind uced resonances are predicted. Variations of the cross-peak intensities dur ing the middle time interval show signatures of exciton population transfer and coherence dynamics. Enhanced resolution is achieved using phase sensit ive detection. (C) 2001 Elsevier Science B.V. All rights reserved.