Resonance fluorescence detection

The kinetics of the reaction of bromine atoms with simple aliphatic aldehydes have been measured by the fast-flow technique with resonance fluorescence detection, and by laser flash photolysis. 

In terms of coupling flame generation and detection methods, several combinations are common. Generally, shock tubes are coupled with IR and UV absorption and gas chromatography (GC) detectors, while flow reactors are used in tandem with GC, electron spin resonance, and resonance fluorescence detection. 

ClO-BrO detector chemical conversion with reagent NO to Cl or Br resonance fluorescence detection of atoms 45... 

Butler et al. (175) measured the LIF spectra of the ground state of the CS radical, and found that it was produced vibra-tionally excited. Their vibrational distribution curve peaks at v" = 3 and extends to v" = 6 (see Figure 10). Their high resolution studies indicated that the rotational population could be described with a "temperature" of about 700 K. Addison et al. (176) directly measured the S(4i) concentration change in time using resonance fluorescence detection. From the time dependence they extrapolated the concentration back to zero time and determined the nascent atom concentration for the 4). The yield of the S(3p)/S(4)) ratio was obtained by measuring the... 

Fig. 13. Cross sectional perspective schematic of the suspended payload showing a cutaway of the detection nacelles with impeller driven flow through chambers, detection head and lamp modules used in the resonance fluorescence detection of radicals.

By the technique of flash photolysis and resonance fluorescence detection of both 0( P) and S( P), an upper limit of 2 percent relative to the yield of S( P) was obtained. 

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... 

The high sensitivity of resonance fluorescence detection of atoms allows the time scale of reactions with rates approaching the bimolec-ular colhsion frequency to be extended into the millisecond range accessible in the scharge-flow method. In this way, rate constants have been measured at 298 K for the very rapid reaction Cl -I- Brg BrCl -f- Br, k = 0 5 Z12 at 298 K, as well as for the following slower reactions ... 

The progress of reaction (80) when Oj was excited viin-ationally was followed by resonance fluorescence detection of the CX P) atoms that were formed as product. On the assumption that V-V equilibration was rapid and that the laser enhancement corresponded to reaction of 03 (010), Kurylo et deduced kmikao) 38 ( 20). If more highly excited states were responsible for the accelerated reaction rate this ratio would increase. With the same assumption r ardlng the vj mode as active, Kaldor et al. found ktdkti) = 2.5. In this case, as with the NO-O3 reaction, chemiluminescence from an electronically excited product could be observed and was used to follow the kinetics of the enhanced reaction. 

Resonance fluorescence detection is a highly sensitive method for observing atomic species. A trace of gas such as hydrogen is mixed with helium and passed into a microwave discharge in which some hydrogen is dissociated ... 

FIGURE 7 Schematic diagram illustrating the various processes occurring during reaction of H atoms with resonance fluorescence detection. [Reproduced with permission from Pilling, M. J., and Seakins, P. W. Reaction Kinetics, Oxford University Press, Oxford.]... 

This reaction was studied at 296 K by Wallington and Kurylo (1987a) using flash photolysis with resonance fluorescence detection of OH. They found a rate coefficient of (1.10 0.09)x 10" cm molecule" s". In the absence of other data, we recommend this value, with an estimated uncertainty of 40%. 

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