Mixed Potential Energy Surfaces of the Ultrafast Isomerization of Retinal in BacteriorhodopsinPhilip J. M. Johnson, Alexei Halpin, Takefumi Morizumi, Valentyn I. Prokhorenko, Oliver P. Ernst and R. J. Dwayne MillerEPJ Web of Conferences, 41 (2013) 07020DOI: https://doi.org/10.1051/epjconf/20134107020