Resonant broadband stimulated Raman scattering in myoglobin

Spontaneous Raman is a well-established tool to probe molecular vibrations. Under resonant conditions, it is a largely used method for characterizing the structure of heme-proteins. In recent years, advances in pulsed laser sources allowed to explore vibrational features with complex techniques based on nonlinear optical interactions, among which is stimulated Raman scattering (SRS). Building on its combined spectral–temporal resolutions and high chemical sensitivities, SRS has been largely applied as a probe for ultrafast, time-resolved studies, as well as an imaging technique in biological systems. By using a frequency tunable, narrowband pump pulse jointly with a femtosecond white light continuum to initiate the SRS process, here we measure the Raman spectrum of a prototypical heme-protein, namely deoxy myoglobin, under two different electronic resonances. The SRS results are compared with the spontaneous Raman spectra, and the relative advantages, such as the capability of our experimental approach to provide an accurate mapping of Raman excitation profiles, are discussed.