Upconversion fluorescence spectroscopy

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... 

Goodson and co-workers investigated excitation energy transfer processes in nitrogen cored distyrylbenzene and triarylamine dendrimer systems (Fig. 1.5) by photon echo and polarized fluorescence upconversion spectroscopy. Observed components of less than 1 ps were attributed to a coherent energy transport mechanism. The contributions from his group were recently summarized [15],... 

Zhang XX, Wiirth C, Zhao L, Resch-Genger U, Emsting NP, Sajadi M (2011) Femtosecond broadband fluorescence upconversion spectroscopy improved setup and photometric correction. Rev Sci Instrum 82 063108... 

Precise measurements of the excited state lifetimes of the DNA constituents were not available till very recently, mainly due to the limited time resolution of conventional spectroscopic techniques. Studying the DNA nucleosides by transient absorption spectroscopy, Kohler and co-workers observed a very short-lived induced absorption in the visible which they assigned to the first excited state [5,6]. The lifetimes observed were all well below 1 picosecond. The first femtosecond fluorescence studies of DNA constituents were performed using the fluorescence upconversion technique. Peon and Zewail [7] reported that the excited state lifetimes of DNA/RNA nucleosides and nucleotides all fall in the subpicosecond time, thus corroborating the results obtained by transient absorption. 

Fig. 11 Illustration of the excited state relaxation derived from experimental results obtained for poly(dA).poly(dT) by steady-state absorption and fluorescence spectroscopy, fluorescence upconversion and based on the modeling of the Franck-Condon excited states of (dA)io(dT)io. In red (full line) experimental absorption spectrum yellow circles arranged at thirty steps represent the eigenstates, each circle being associated with a different helix conformation and chromophore vibrations.

The methods discussed so far, fluorescence upconversion, the various pump-probe spectroscopies, and the polarized variations for the measurement of anisotropy, are essentially conventional spectroscopies adapted to the femtosecond regime. At the simplest level of interpretation, the information content of these conventional time-resolved methods pertains to populations in resonantly prepared or probed states. As applied to chemical kinetics, for most slow reactions (on the ten picosecond and longer time scales), populations adequately specify the position of the reaction coordinate intermediates and products show up as time-delayed spectral entities, and assignment of the transient spectra to chemical structures follows, in most cases, the same principles used in spectroscopic experiments performed with continuous wave or nanosecond pulsed lasers. 

Soukka T, Rantanen T, Kuningas K (2008) Photon upconversion in homogeneous fluorescence-based bioanalytical assays. Ann N Y Acad Sci 1130 188-200, Fluorescence Methods and Applications Spectroscopy, Imaging, and Probes... 

In fluid solvents at room temperature, spectral relaxation is usually comjdete prior to emission and occurs within abont 10 ps. This process is too rapid to be resolved with the usual instrumentation for TD or FD fluorescence. However, advances in laser technology and methods for ultrafast spectroscopy have resulted in an increasing interest in picosecond and femtosecond solvent dynaaiics. Becmise of the rapid timescale, the data on solvent dynamics are usually obtained using flurvescence upconversion. Hiis method is described in Section 4.7.C. lypical data are... 

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