Abstract
A measurement system for ultrafast time-resolved fluorescence spectroscopy was constructed based on electronic Kerr effect. Suitable Kerr medium was searched among glasses and isotropic single crystals by using the Z-scan method that can evaluate two-photon absorption coefficient and photo-induced refractive index change. With optimization of design of the optical system, we achieved the time resolution of 180 femto-second, 5 % gating transmittance and the one-order-faster data acquisition than conventional method. Time-resolved spectra were measured for photoactive yellow protein (PYP). The Kerr-gating system enabled for the first time to obtain the 2-dimensional, time-wavelength mapping of time-resolved fluorescence spectra in the femto-pico-second time region. Vibrating behavior of fluorescence intensity peak was clearly recognized, which is curious and has never seen in dye solution systems at room temperature. It suggests that, in PYP, chromophore is energetically isolated from the main structure of amino-acid chain and that photo-excited energy is dissipates through specific channels.
