Lack of evidence for one-photon coherent control of the primary photoisomerisation in retinal proteins

The concept of shaping electric fields to coherently steer light induced processes has fascinated scientists for decades. Despite early theoretical considerations ruling out one-photon coherent control, several experimental studies have reported excitation field shape dependent molecular responses in the weak-field limit. These observations were largely attributed to the presence of rapid decay channels, but experimental verification is lacking. Here, we rigorously test this hypothesis by investigating the degree of achievable control over the photoisomerisation of the retinal protonated Schiff base in bacteriorhodopsin, isorhodopsin and rhodopsin, all of which exhibit similar chromophores but different isomerisation yields and excited state lifetimes. Irrespective of the system studied, we find no evidence for dissipation-dependent behaviour, nor for any coherent control in the strict one photon limit. Our results raise the question to which extent a photochemical process at ambient condition can be controlled at the amplitude level and how the underlying molecular potential energy surfaces and dynamics may influence this controllability