Emission intensity, measurement

Relative emission Intensity measurements were made at 475 nm for tin analysis, the emission maximum for the tln-flavonol complexes examined In this work. Emission spectra are uncorrected. 

Characteristic X-rays emitted from transitions involving K and L electrons wavelength and emission intensity measurements for qualitative and quantitative elemental analysis respectively. 

The authors made no attempt at quantitative emission-intensity measurements. They did make the qualitative observation, however, that the rare-earth-ion emissions from the D20 solvated crystals were much more intense than the emissions from the H20 solvated ones. 

Kummler68 reports a private communication from Mahan which suggests that the rate constant for the reaction between 02(1A9) and ethylene is slower, but not more than ten times slower, than the reaction between atomic oxygen and ethylene. Thus the rate constant should be between about 2 x 107and2 x 108 liter mole-1 sec-1. Absolute measurements of the reactivity of singlet oxygen with olefins have recently been made by Broadbent et al.,51 using both emission intensity measurements and the rate of reactant removal, to follow the reaction. A preliminary rate constant of 2.3 x 105 liter mole-1 sec-1 has been obtained for the reaction... 

Even if equilibrium is achieved in the excited state, the lifetime effect always remains in emission intensity measurements. If the experimentally determined quantity on the left of (28) is regarded as the approximate p/iT(S x)-value, the compound will appear to be a weaker acid than it really is i.e. too much BH+(S ) will seem to be present if BH+(S ) has the shorter lifetime, or a stronger acid if B(S ) has the shorter lifetime. The rule is that the species of shorter lifetime produces a greater emission than would be expected from the equilibrium concentrations, because its concentration is depleted more rapidly and is therefore replenished all the time from the longer-lived species in an attempt to maintain the equilibrium. 

Despite the fact that emission intensity measurements require supplementary lifetime determinations, they have the advantage over laser flash absorption techniques that they by-pass complications due to absorption by secondary products, such as radicals or solvated electrons (see e.g. Klaning et al., 1973). 

We referred in the last paragraph to the calculation of concentrations of excited species from emission intensity measurements, ft may, however, not always be possible to determine Am directly, and some other method of evaluating A factors may be needed. The A coefficient may be calculated from the B coefficient for the same transition by using the relation... 

The transition dipole mn in Eqs. [136] and [139] is the gas-phase adiabatic transition dipole. Therefore, emission intensities measured in different solvents should generate invariant transition dipoles when treated according to Eqs. [136] and [139]. A deviation from invariance can be used as an indication of the breakdown of the two-state approximation and the existence of intensity borrowing from other excited states of the chromophores (the Murrell mechanism T88,94j Figure 16 illustrates the difference between Eq. [139] and... 

Sulzmann et al. [386] have studied the onset of CO2 formation behind incident shock waves in CO/O2 /Ar mixtures containing about 80 % ai on by means of emission intensity measurements at 3064 and 4470 A, and also at 4.25 and 5.07 pm. They also investigated the influence of hydrogen on the induction period [387]. Temperatures were in the range 1500—3000 K. In comparing the results of the experiments with an analytical expression for the induction times, they considered reaction (Ixii) to be the initiating step in both cases, viz. 

Experimentally the technique is simple since the sample may be irradiated from time to time and the emission intensity measured by a photomultiplier over a period of tens of seconds (Lange et al, 1998). However, these studies confirmed the limited usefulness of CRL alone for real-time monitoring since the emission is significant only in the glassy state, so this technique cannot detect the gel point for the majority of networks. When combined with other luminescence methods it has potential use because it is independent of the atmosphere and is readily adaptable to fibre-optics. 

Janssen (Jl) suggested that spectral analysis, until then used only for qualitative observations, was suitable also for quantitative work. He felt that such a development would be particularly advantageous in the case of elements like sodium which were difficult to determine by classic procedures. His suggestions bore fruit 3 years later when Champion et al. (Cl) constructed an instrument for the determination of sodium in plant ash. A solution of plant ash was introduced into the flame by means of a platinum wire and the emission intensity measured by comparing it by means of a visual photometric attachment with light from a reference constant-intensity sodium flame. This spectronatrometre was the first flame photometer and when one considers that it was capable of an accuracy of between 2 and 5 %, it is interesting that it was not for more than 70 years that the method was applied to clinical problems. 

A bottle of tonic water is to be analyzed for its quinine content by fluorescence spectrometry, with excitation at 350 nm and emission intensity measured at 430 nm. One milliliter of tonic water is diluted to 100 ml with 0.05 M HaS04 its emission Intensity is 8.44 (arbitrary units). A series of quinine standards, in 0.05 M HaSO, is prepared and the emission intensities measured (in parentheses) 100 ppm (293 units), 10.0 ppm (52.3), 1.00 ppm (12.0), 0.100 ppm... 

The luminescence excitation spectra shown in Fig. 8 do not clarify the picture although one can observe the same rank ordering in the emission intensity (measured at Ams = 505 nm) as with the emission spectra except for the D2 molecule having the lowest value. This appears plausible considering that if interaction effects were essentially localized between two adjacent aromatic groups the behavior of the large ring should be very similar to that of the short linear molecule. 

Fig. 16 Nonisothermal evolution in CL emission intensity measurements for PP modifies with palm fiber (29 %) after weathering. The data were taken from [05A1].

A sample portion is weighed and diluted by mass with mixed xylenes or other solvent. An internal standard, which is requii, is either weighed separately into the test solution or is previously combined with the dilution solvent Calibration standards are prepared similarly. The solutions are introduced to the ICP instrument by free aspiration or an optional peristaltic pump. By comparing emission intensities of elements in the test qjedmen with emission intensities measured with the calibration standards and by applying the appropriate internal standard correction, the concentrations of elements in the sample are calculable. 

Fig. 18. Arrhenius plots for the emission intensities measured at the electronic origins II and I of [Rufbpy-hjlj] in [Zn(hpy-hg)3J(C104)2. The intensity ratio determined from usual, time-integrated emission spectra strongly deviates from a Boltzmann distribution below = 2.2 K due to relatively slow thermalizations, while the intensity ratio determined from time-delayed spectra (t = 10 ps, At = 300 ps) follows strict Arrhenius behavior according to the expression given. k , represent the radiative rates for the purely electronic (0-0) transitions (at the electronic origins). The error is smaller than the size of the experimental points. The curve shown for the time-integrated data is calculated from values known for decay rates, sir rates, and...

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