Ultrafast transient absorption of eumelanin suspensions: the role of inverse Raman scattering.
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.
Department of Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari Aldo Moro, Piazza G. Cesare 11, 70124, Bari, Italy ; Institute for Complex Molecular Systems, Eindhoven University of Technology, Post Office Box 513, 5600MD Eindhoven, The Netherlands ; Laboratory of Macromolecular and Organic Chemistry, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Postoffice 513, 5600MD Eindhoven, The Netherlands.
Antonio
A
Aloi
Department of Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari Aldo Moro, Piazza G. Cesare 11, 70124, Bari, Italy.
Adalberto
A
Brunetti
Department of Clinical and Experimental Medicine, University of Foggia, Via Napoli 20, 71122 Foggia, Italy.
Giuseppe
G
Perna
Department of Clinical and Experimental Medicine, University of Foggia, Via Napoli 20, 71122 Foggia, Italy.
Maria
M
Lasalvia
Department of Clinical and Experimental Medicine, University of Foggia, Via Napoli 20, 71122 Foggia, Italy ; Istituto Nazionale di Fisica Nucleare, Sez. di Bari, Via Orabona 4, 70125 Bari, Italy.
Vito
V
Capozzi
Department of Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari Aldo Moro, Piazza G. Cesare 11, 70124, Bari, Italy ; CNR-IPCF Bari Div., c/o Chemistry Department, via E. Orabona 4, 70125 Bari, Italy.
Raffaele
R
Tommasi
(160.1435) Biomaterials; (190.5890) Scattering, stimulated; (300.6240) Spectroscopy, coherent transient; (320.7150) Ultrafast spectroscopy