Spectrally resolved femtosecond 2-colour 3-pulse photon echoes: a new spectroscopic tool to study molecular dynamics

Abstract

We present a new multidnuensional femtosecond spectroscopy technique based on spectrally resolved 2-colour 3-pulse photon echoes for investigating molecular dynamics iii a vanety of systems including proteins. In this technique the sample is illuniinated by two feintosecond ‘pump’ pulses with wave vectors k₁, k₂ and wavelength λ_pump and a femtosecond ‘probe’ pulse with wave vector k₃ and wavelength λ_probe. Nonlinear signals are generated in the phasematching directions k₄=−k₁+k₂+k₃ and k₆=−k₁+k₂. These signals are analysed in spectrometers equipped with CCD detectors and the spectra of the signals are recorded for various values of (i) the delay t₁₂ between pulses 1 and 2, (ii) the delay t₂₃ between pubes 2 and 3, and (iii) die wavelengths λ_pump, λ_probe. The technique has been used for studying vibrational and electronic dynamics of dye molecules, such as cresyl violet ni methanol, and ultra-fast transient processes that occiur diring the photo-dissociation of carbonmonoxy myoglobmn (MbCO) into mnyoglobin (Mb) and CO.