Femtosecond spectroscopy of the photoisomerisation of the protonated Schiff base of all-trans retinal

The light-induced isomerisation reaction of the protonated Schiff base retinal molecule in solution (PSBR-s) was studied by femtosecond absorption spectroscopy. After electronic excitation, ultrafast reactions on the excited electronic state occur on a 100 fs time-scale. The decay of S-1 exhibits a biphasic dependence with a 2.0 and a 7.2 ps process. The photoreaction of PSBR-s is compared with the processes found in the retinal proteins rhodopsin, bacteriorhodopsin and halorhodopsin.