This loss provides a thermal barrier to the equilibration of the intermediates with the excited state and thus minimizes loss of the excitation energy and increase of efficiency of energy storage. The discussion will be restricted to the efficiency of the primary reaction of energy storage. Given this simple view, the only relevant parameter is the energy of the absorbed photons, as Parson (1978) has indicated. To be thermodynamically specific, this energy is an enthalpy since the energy of the light beam is always ultimately measured as the heat liberated on total absorption MK-0518 nmr and decay.

This also follows from the simple view of loss of memory on absorption. Quantum meters are generally unavailable since all detectors have unknown absolute sensitivity, which usually varies with wavelength. Thus the number flux of photons in the light beam is simply the energy flux divided by Planck’s constant times the frequency, with a suitable average over the distribution of frequencies if required. The much-used notion of the temperature of a photon flux is valid only for the black body distribution of frequencies, since this is an equilibrium situation with a well-defined temperature, the

thermodynamic temperature. All other “temperatures” depend on definitions. In any case, they are irrelevant as the simple view states. Essentially, the absorption of a photon—at the intensities https://www.selleckchem.com/products/MK-2206.html and for molecules relevant to photosynthesis—is an irreversible process, and its description as an equilibrium Thiazovivin supplier process leads to the aforementioned confusion. Free energy and equilibrium Rutecarpine The free energy of a process can only be defined for the process at equilibrium. Measuring the free energy via the redox potentials of short-lived excited states is difficult,

requiring electron transfer equilibrium to be obtained during the lifetime of the state. For simple molecules in a non-reactive environment, the energy of the equilibrated excited state is usually taken to be the crossing point of the normalized absorption and fluorescence spectra. This is required because of the Stokes shift in polyatomic molecules. This shift measures the difference of the vibe-rot-librational frequencies, including interactions with the solvent, between the ground and excited states of the molecule and their differing interactions with the surrounding medium. It can be small (e.g., ~0.03 eV for chlorophyll) or large (e.g., ~1 eV for some aromatic amines used as polarity “reporter” groups). [Note that one way to obtain an efficiency >100 % is to excite the molecule at a frequency less than the maximum of the fluorescence emission band. In this case, thermal energy is used to re-equilibrate the excited state. This is the method used to prepare ultra cold gas atoms (Bose condensates) and has even been observed in the liquid phase with rhodamine 6G (Zander and Drexhage 1995). Our recent measurements on the chlorophyll d containing A.