Stimulated infrared emission in all-trans retinal and wild-type bacteriorhodopsin under CW optical pumping: Studies by FT-IR spectroscopy

Here we demonstrate FT-IR emission spectroscopy, which is a technique that utilizes the CW optical pumping in order to prepare and monitor vibrtaionally excited states of samples. Emission spectra of the both, all-trans retinal and bacteriorhodopsin, have demonstrated the extremely high-sensitivity to the changes in the illumination conditions. We assume that such spectral behavior is the result of the complex nature of the states involved in IR-transitions. One would expect that even relatively small changes in coordination geometry would have a significant effect on the infrared spectra. This approach is a particularly useful for the detection of the previously unknown vibrational modes. It appears possible, that the IR-emission spectral data needed for a precise vibrational assignment of the bR's structure can be available.