Femtosecond fluorescence upconversion

Underwood, D. E., Kippeny, T. and Rosenthal, S. J. (2001) Ultrafast carrier dynamics in CdSe nanocrystals determined by femtosecond fluorescence upconversion spectroscopy. /. Phys. Chem. B, 105,436-443. 

Gustavsson T, Sharonov A, Markovitsi D (2002) Thymine, thymidine and thymidine 5 -monophosphate studied by femtosecond fluorescence upconversion spectroscopy. Chem Phys Lett 351 195... 

Gustavsson T, Sarkar N, Lazzarotto E, Markovitsi D, Improta R (2006) Singlet excited-state dynamics of uracil and thymine derivatives a femtosecond fluorescence upconversion study in acetonitrile. Chem Phys Lett 429 551-557... 

Wang H, Zhang H, Abou-Zied OK et al (2003) Femtosecond fluorescence upconversion studies of excited-state proton-transfer dynamics in 2-(20-hydroxyphenyl)benzoxazole (HBO) in liquid solution and DNA. Chem Phys Lett 367 599-608... 

Fujino, T., and Tahara, T. 2004. Characterization and performance of femtosecond fluorescence upconversion microscope. Appl. Phys. B 79 145. 

Femtosecond fluorescence upconversion studies of chiral self-assembled supramolecules in solution... 

Sample preparation was given elsewhere [2]. Femtosecond fluorescence upconversion and picosecond time-correlated single-photon-counting set-ups were employed for the measurement of the fluorescence transients. The system response (FWHM) of the femtosecond fluorescence up-conversion and time-correlated single-photon-counting setups are 280 fs and 16 ps, respectively [3] The measured transients were fitted to multiexponential functions convoluted with the system response function. After deconvolution the time resolution was 100 fs. In the upconversion experiments, excitation was at 350 nm, the transients were measured from 420 nm upto 680 nm. Experiments were performed under magic angle conditions (to remove the fluorescence intensity effects of rotational motions of the probed molecules), as well as under polarization conditions in order to obtain the time evolution of the fluorescence anisotropy. 

To reveal possible ultrafast processes occurring on a time scale less than 30 ps, femtosecond fluorescence upconversion experiments were performed [30] in toluene under magic angle polarization. To extract complete information of the decay times and their amplitudes in function of detection wavelength, the measurements were performed in three time windows of 5 ps, 50 ps, and 420 ps. 

The short time scale dynamics have been studied by means of femtosecond fluorescence upconversion. For all dendrimers these measurements revealed size-independent kinetic processes related to an internal vibrational redistribution, a vibrational/solvent relaxation. Singlet-singlet annihilation, only present in the multichromophoric compounds, was established by an excitation energy-dependent study. It has been shown that this type of process contributes to a larger extent in the para-substituted dendrimers compared to the meta-substituted ones. These differences between the meta- and para-substituted dendrimers... 

Figure 11.8 Schematic view of the experimental setup for the femtosecond fluorescence upconversion spectrometer. DM, dichroic mirror used to separate the second harmonic (394 nm) from the fundamental (788 nm) HW, half-wave plate used to control...

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