Abstract-It is experimentally verified that a synchroscan streak camera, incorporating a microchannel plate and synchronizing with UV picosecond pulses generated inside the cavity of a mode-locked CW ring dye laser, has enough sensitivity to detect picosecond emission phenomena in the region ofasingle-photon event. To demonstrate the usefulness of the synchroscan streak camera, the first measurement of time-and wavelength-resolved emissions in the picosecond region is successfully carried out for adenine and polyadenylic acid aqueous solutions at room temperature, and shows that their shortest lifetimes, due to the monomer fluorescence, are 6 and 8 ps, respectively.F OR a study on nucleic acid photochemistry and photobiology, it is essential to make clear the dynamic behavior of the luminescence from nucleic acid bases in mononers, polymers, and higher order structures. photon counting method. They found that the emission quantum yields of adenine and polyadenylic acid were 2.4 X and 3 X respectively [3 J . The lifetime of polyadenylic acid depended on the wavelength of the emission band, and the origin of more than three emission components was discussed 131. However, the questions still remain because of the instrumental restriction of the time resolution. Therefore, further investigation based on time-and wavelength-resolved emission measurements in the picosecond time region is strongly needed.An electron-optical streak camera in synchronous operation with a mode-locked CW dye laser has become the most useful instrument that can directly measure the time and wavelength versus the intensity profile of a picosecond optical event for the weak luminescence [5], [6]. Using a highly-sensitive synchroscan streak camera with a mode-locked and internally frequency-doubled CW ring dye laser, we report the first direct
We report on the demonstration of the femtosecond nonlinear optical response from a two-dimensional monomolecular layer of squarylium dye J aggregate at 5 °C. The formation of a monomolecular layer Langmuir film was achieved by spreading squarylium dye modified by two propyl and two hexyl groups at the air–water interface, which resulted in a very strong J band (o.d.=0.3) at 777 nm. The transient absorption spectra in a resonant pump-probe measurement showed a low absorption saturation power (9.7×106 W/cm2) and an ultrafast response (300 fs), which are indicative of exciton delocalization over 18 molecules in this J aggregate, even at 5 °C.
By using a highly sensitive streak-camera technique, we investigate incorporation processes of HpD into malignant tumor m-KSA cells in vitro. The picosecond decays of the total fluorescence spectra, the wavelength-resolved fluorescence decays and the time-resolved fluorescence spectra from HpD in the cells are measured as a function of the incubation time. The results show that the aggregate component of HpD which has a fast fluorescence lifetime of 100 ps and a red-shifted band of -660 nm selectively accumulates more and more in the cells with the increase of the incubation time.Photobiol. 39, 851-859.
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