title: Spectral watermarking in femtosecond stimulated Raman spectroscopy: resolving the nature of the carotenoid S* state.
abstract: A new method for recording femtosecond stimulated Raman spectra was developed that dramatically improves and automatizes baseline problems. Instead of using a narrowband Raman source, the experiment is performed using shaping of a broadband source. This allows locking the signal into carefully crafted watermarks that can be recovered from measured data with high fidelity. The approach uses unique properties of Raman scattering, thus allowing a direct recording of stimulated Raman signals with robust rejection of baselines and fixed-pattern-noise. Low cost technology for generating required pulse-shapes was developed and demonstrated. The methodology is applicable to any Raman experiment but primarily targets Femtosecond Stimulated Raman spectroscopy (FSRS) where a lack of robust methods for parasitic signal rejection has been a major obstacle in the practical development of the field in the last decade. The delivered improvement in FSRS experiments was demonstrated by recording evidence that the so-called S* state of carotenoids in solution corresponds to the optically forbidden S1 state of a sparsely populated carotenoid conformation.
authors.affiliation: Department of Physics and Astronomy, VU University Amsterdam, De Boelelaan 1081, 1081HV Amsterdam, The Netherlands. miroslav.kloz@eli-beams.eu and ELI-Beamlines, Institute of Physics, Na Slovance 2, 182 21 Praha 8, Czech Republic.
authors.forename: Miroslav
authors.initials: M
authors.lastname: Kloz
authors.affiliation: Department of Physics and Astronomy, VU University Amsterdam, De Boelelaan 1081, 1081HV Amsterdam, The Netherlands. miroslav.kloz@eli-beams.eu.
authors.forename: Jörn
authors.initials: J
authors.lastname: Weißenborn
authors.affiliation: University of South Bohemia, Branišovská 1645/31a, 370 05 České Budějovice, Czech Republic.
authors.forename: Tomáš
authors.initials: T
authors.lastname: Polívka
authors.affiliation: Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Storrs, CT 06269, USA.
authors.forename: Harry A
authors.initials: HA
authors.lastname: Frank
authors.affiliation: Department of Physics and Astronomy, VU University Amsterdam, De Boelelaan 1081, 1081HV Amsterdam, The Netherlands. miroslav.kloz@eli-beams.eu.
authors.forename: John T M
authors.initials: JT
authors.lastname: Kennis
mesh_terms: D002338:Carotenoids / Q000737:chemistry*; D059629:Signal-To-Noise Ratio; D013059:Spectrum Analysis, Raman; D013997:Time Factors; D024341:Xanthophylls / Q000737:chemistry; D019207:beta Carotene / Q000737:chemistry
chemical_list: D024341:Xanthophylls; D019207:beta Carotene; D002338:Carotenoids; C055255:spirilloxanthin