Fluorescence gating

For cases where the non-aperture flux dominates, fluorescence gating can provide a large background reduction. Measurements of the ratio of pair... 

Hard X-rays detectors can also be divided in two broad classes gas filled proportional counters (Ubertini, 1987) and scintillation detectors, the latter type being successfully implemented at energies higher than a few tenths of keV. Currently, the availability of space-qualified, high pressure gas cells and the outcome of the fluorescence gating technique for background rejection, have made proportional counters efficient up to < 200 keV. 

Fig. 1.5 Fluorescence emission spectrum of the luciferase-oxyluciferin complex in the same solution as in Fig. 1.4 (solid line), compared with the luminescence spectrum of firefly luciferin measured in glycylglycine buffer, pH 7.6 (dotted line). The former curve from Gates and DeLuca, 1975 the latter from Selinger and McElroy, 1960, both with permission from Elsevier.

Raman scattering is essentially undelayed with respect to the arrival of the incident light, in this technique the detector is activated only during each laser pulse and deactivated at all other times. This allows only Raman signals to be recorded but fluorescence signals and detector noise are gated out (Fig. 19). Improvement in Raman signal to fluorescence ratio has been achieved as illustrated in Fig. 20. The technique, however, at present seems to be restricted by several instrumental limitations [37). 

Employing all of the TR results in conjunction with results from femtosecond time-resolved transient absorption (fs-TA) and femtosecond time-resolved Kerr gated fluorescence (fs-KTRF) experiments enables a reaction mechanism to be developed... 

Kosumi, D., K. Yanagi, R. Fujii, H. Hashimoto, and M. Yoshizawa. 2006. Conjugation length dependence of relaxation kinetics in beta-carotene homologs probed by femtosecond Kerr-gate fluorescence spectroscopy. Chem. Phys. Lett. 425 66-70. 

Lada, M.W., Kennedy, R.T. (1996). Quantitative, in vivo monitoring of primary amines in rat caudate nucleus using microdialysis coupled by a flow-gated interface to capillary electrophoresis with laser-induced fluorescence detection. Anal. Chem. 68, 2790-2797. 

HPLC with microchip electrophoresis. Capillary RPLC was used as the first dimension, and chip CE as the second dimension to perform fast sample transfers and separations. A valve-free gating interface was devised simply by inserting the outlet end of LC column into the cross-channel on a specially designed chip. Laser-induced fluorescence was used for detecting the FITC-labeled peptides of a BSA digest. The capillary HPLC effluents were continuously delivered every 20 s to the chip for CE separation. 

Lapos JA, Ewing AG (2000) Injection of fluorescently labeled analytes into microfabricated chips using optically gated electrophoresis. Anal Chem 72 4598-4602... 

The experiment is performed with a spectrofluorometer similar to the ones used for linear fluorescence and quantum yield measurements (Sect. 2.1). The excitation, instead of a regular lamp, is done using femtosecond pulses, and the detector (usually a photomultiplier tube or an avalanche photodiode) must either have a very low dark current (usually true for UV-VIS detectors but not for the NIR), or to be gated at the laser repetition rate. Figure 11 shows a simplified schematic for the 2PF technique. 

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