Open AccessUltrafast transient absorption of eumelanin suspensions: the role of inverse Raman scattering
Author(s) -
Antonio Aloi,
Adalberto Brunetti,
G. Perna,
Maria Lasalvia,
V. Capozzi,
R. Tommasi
Publication year - 2015
Publication title -
biomedical optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.362
H-Index - 86
ISSN - 2156-7085
DOI - 10.1364/boe.6.004000
Subject(s) - photoexcitation , raman scattering , ultrashort pulse , femtosecond , ultrafast laser spectroscopy , materials science , absorption (acoustics) , scattering , relaxation (psychology) , raman spectroscopy , optics , chemical physics , molecular physics , analytical chemistry (journal) , chemistry , laser , atomic physics , physics , excited state , chromatography , psychology , social psychology , composite material
An ultrafast investigation is carried out on synthetic eumelanin suspended either in water or in DMSO-methanol. Upon photoexcitation by visible femtosecond pulses, the transient absorption (TA) dynamics of the suspensions are probed in a broad visible spectral range, showing clear nonlinearities. The latter arise from pump-probe interactions that induce the inverse Raman scattering (IRS) effect. We show how eumelanin TA dynamics are modified in proximity of the solvent Stokes and anti-Stokes scattering peaks, demonstrating that IRS affects the sign of TA but not the relaxation times. We compare the results obtained in both suspensions, unveiling the role of the surrounding environment. Eventually, the intrinsic response of synthetic eumelanin to ultrafast photoexcitation is evaluated.