Almost every known visual process is based on one specific molecule, the Retinal Protonated Schiff Base Chromophore (RPSB), which has remarkable photo properties. The RPSB has a tunable absorption, and is used by different Rhodopsin proteins which absorb light in different parts of the visible spectrum. Absorption of a photon causes the molecule to isomerize, thus converting the photon energy into a mechanical action. This photo-isomerization occurs with a high efficiency, and specifically around one specific bond. In the attempt to understand these basic quantum mechanical processes we study the RPSB in the gas phase, where it is completely isolated from the surroundings. This allows us to produce data that can be directly compared with theory and provides detailed information about the dynamics and thermodynamics of the chromophore. In this talk we will present measurements of the heat capacity and of the fragmentation mechanism of the RPSB, and discuss future plans for directly measuring the photoisomerization of isolated RPSB's.

[1] "Probing the barrier of internal rotation of the retinal chromophore” Y. Toker, A. Svendsen, A. V. Bochenkova, L. H, Andersen; Angew. Chem. Int. Ed. 51 (2012), 8757.

[2] “Photoresponse of the protonated Schiff-base retinal chromophores in the gas phase”  Y. Toker, D. B. Rahbek, H. V. Kiefer, J. Rajput, R. Antoine, P. Dugourd, S. Brønsted Nielsen, PCCP 15 (2013), 19566.