Pulsed fluorescence method

Sulfur Dioxide. Both flame photometric and pulsed fluorescence methods have been applied to the continuous measurement of S02 from aircraft. In the flame photometric detector (FPD), sulfur compounds are reduced in a hydrogen-rich flame to the S2 dimer. The emission resulting from the transition of the thermally excited dimer to its ground state at 394 nm is measured by using a narrow band-pass filter and a photomultiplier tube. 

Fig. 12. Experimental arrangement for the measurement of pulse widths of ultrashort pulses by the two-photon fluorescence method. B, beam splitter. Mi, 2, mirrors, DC, dye cell containing fluorescing dye solution that absorbs at half the laser wavelength, C, camera...

Very recently. LET effects on fluorescence lifetimes of low molecular polyethylene model compounds (n-alkane) have been studied by many kinds of pulse radiolysis - methods such as electron beam, ion beam and synchrotron radiation (SR) [40] pulse radiolysis techniques [41]. Figure 10 shows time profiles of the fluorescence from neat n-dodecane liquids irradiated many kinds of radiation with different LET. The fluorescence lifetimes from irradiated neat... 

The initial charge separation in PS I and PS II can be followed by what are known as ultrafast optical spectroscopy techniques. Several variations on this method exist, but they can be grouped into pump-probe absorbance difference and transient fluorescence methods (25, 26). In the first instance, the sample is irradiated with a pump pulse to initiate the electron transfer and the absorbance is measured using a probe pulse at a... 

The pulse fluorimetric method, however is applicable only when one species has a much longer decay time than other species in the solution, it is much less useful when several species in solution have similar decay times. The pulse fluorimetric approach has only limited application to the resolution of more than two fluorescers under any circumstances. 

Combining the above described microfluidic differential resistive pulse sensor method with a miniature laser-fiber optic fluorescent detector, the simultaneous detection of fluorescent and non-fluorescent particles has been demonstrated [19], This method is simple, inexpensive, and easy to operate, and can achieve highly sensitive and accurate detection without relying on any conventional bulky instmments. Excellent agreement was achieved by comparing the results obtained by this chip system with the results from a commercial flow cytometer for a variety of samples of mixed fluorescent and non-fluore scent particles. 

For solutions of naphthalene in cyclohexane the yield of triplet states of naphthalene, the intensity of monomer and excimer fluorescence, and the yield of singlet state naphthalene have been measured as a function of naphthalene concentration by pulse radiolysis methods. The influence of a number of electron scavengers on these yields has been determined... 

Stuhl, F., and H. Niki (1972). Pulsed vacuum uv-photochemical study of reactions of OH with H2, D2 and CO using a resonance-fluorescence method. J. Chem. Phys. 57, 3671-3677. 

The method s sensitivity can be estimated by following up the previous example. Assuming a fluorescence quantum yield of 0.1 and a spatial collection efficiency of 10 , a population of 5x10 excited molecules leads to 5 X 10 photons reaching the detector per pulse. Single-photon counting techniques easily allow the observation of 0.1-1 photon per pulse. Evidently fluorescence methods can easily be used to probe submil-litorr samples. 

In the present work, a new kinetics configuration utilizing a pulsed laser for photolysis and a quasi-cw, ultraviolet laser for fluorescence excitation has been developed. This technique combines the best features of the two kinetic methods mentioned above. Laser photolysis generally permits greater reactant formation specificity than does flashlamp photolysis. Laser-induced fluorescence detection outperforms resonance fluorescence detection because of its increased fluorescence excitation flux, decreased scattered light signal, and wavelength tunability. Cw fluorescence excitation is desirable over pulsed fluorescence excitation due to its freedom from pulse-to-pulse normalization constraints and, most importantly, because of its efficient duty cycle and the consequent increased density of points obtainable... 

More recently, Natrajan and Christensen [10] considered the development of a two-dye fluorescence method for temperature measurement using a pulsed, Nd YAG laser as the illumination... 

Kinetic study of OH reactions with H2O2, C3H8 and CH4 using the pulsed photolysis laser induced fluorescence method,... 

This observation should simplify application of fluorescence methods to the estimation of steady-state electron transport rates by eliminating the need to conduct an empirical calibration for each plant studied. However, it is necessary to use a more complex experimental protocol, and in some instances it may be preferable to use a pulse of constant intensity and conduct empirical calibration experiments with that particular tissue. The present work does not preclude such an approach. However, it should be recognized that the values of qp and qj, so obtained, do not provide an accurate indication of the quenching of absorbed photons, and that the apparent dependence of electron transport on these parameters (Eqn. 3) may differ from leaf to leaf and may be non-linear. 

TPA cross-section 1 GM = 10 ° cm sec photon" measured in two-photon fluorescence method with 80 fs pulse laser. Fluorescence quantum yield determined relative to fluorescin in 0.1 N NaOH. 

W.H. Glenn Theory of the two-photon absorption-fluorescence method of pulse width measurement. IEEE J. QE-6, 510 (1970)... 

---