Chemiluminescence emission spectra

Figure 9. Chemiluminescence emission spectra from the two pulses with DPA as the acceptor inset is DPA fluorescence spectrum. (Reproduced from Ref. 24. Copyright 1986 American Chemical Society.)...

There is experimental evidence that triplet states indeed play an important role in radical ion reactions. The formation of excimers has been suggested on the basis of chemiluminescence emission spectra, e.g. in the case of N-phenylcarbazole 15> and in some other experiments 18>. Other authors 19>20> have observed that the excimer fluorescence reported is probably produced by decomposition products of the radical ions or other impurities, as is very probably the so-called preannihilation chemiluminescence which occurs in electrogenerated chemiluminescence (see 21>). 

Chemiluminescence emission spectra and real-color photographs of green chemiluminescence emission from glass and SIFs. M- Metal. 

Table I summarizes the primary features of the chemiluminescent emission spectra obtained from the reaction of ozone with 14 simple olefins. The observed spectra fall into three classes which correlate somewhat with the olefin structure. Class A in Table I includes the three terminal olefins studied all gave a broad, weak emission, peaking at about 440 nm. Figure 2 shows the spectrum obtained in the reaction of ozone with ethylene, a typical member of class A, at a total pressure of 0.4 torr. The emission spectrum may result from excited formaldehyde [emission...

The extreme sensitivity of photon-detection techniques makes possible the measurement of chemiluminescent reactions whose quantum yields may be as low as 10 . Therefore it is essential, if these chemiluminescences are to be related to some physiological or biochemical processes, to be able to identify the nature of the reactions and the reactants. In many cases the yields of products are outside of the range of assay by microanalytical chemistry. In these cases, despite the uncertainties described in Section II above, the only remaining analytical technique is the comparison of the precise shapes of the chemiluminescence emission spectra with the photoexcited fluorescence emission spectra of proposed product molecules and the induction from these data of the substrate molecules and the mechanisms or pathways of the oxidation reactions. ... 

The chemiluminescent emission spectrum of GeCl2 was obtained by burning GeCl4 in potassium vapor using a diffusion flame technique 11 The spectrum consisted of a series of closely spaced diffuse bands in the region 4900—4100 A with an underlying continuum. The bands resemble those of SnCl2. 

Activated chemiluminescence is observed from these secondary peroxy-esters as well. When the thermolysis of peroxyacetate [281 in benzene solution is carried out in the presence of a small amount of an easily oxidized substance the course of the reaction is changed. For example, addition of N,N-dimethyldihydrodibenzol[ac]phenazine (DMAC) to peroxyester [28] in benzene accelerates the rate of reaction and causes the generation of a modest yield of singlet excited DMAC. This is evidenced by the chemiluminescence emission spectrum which is identical to the fluorescence spectrum of DMAC obtained under similar conditions. Spectroscopic measurements indicate that the DMAC is not consumed in its reaction with peroxyester 28 even when the peroxyester is present in thirty-fold excess. The products of the reaction in the presence of DMAC remain acetophenone and acetic acid. These observations indicate that DMAC is a true catalyst for the reaction of peroxyacetate 28. The results of these experiments with DMAC, plotted according to (27) give k2 = 9.73 x 10-2 M-1 s-1. 

Class B in Table I includes seven olefins, which are characterized by dialkyl substitution at one of the carbons of the olefinic double bond. The emission spectrum produced by reaction of these olefins with ozone is characterized by a narrow band peaking at about 520 nm with broad shoulders at 465 nm and 565 nm. Figure 3 gives the chemiluminescent emission spectrum obtained by reaction of a typical member of Class B, tetramethylethylene, with ozone at a pressure of 0.8 torr. It is similar to the fluorescent emission spectrum of biacetyl [broad emission from 440-495 nm (11)1 combined with the phosphorescent emission of the same compound [narrow peaks at about 512 and 561 nm and a broad... 

Fig. l.A. Fluovesoenae and absorption spectra (full lines) of 3-aminophthalio acid (10 M) in aqueous solution (pH 11.6) 0.1 M K2C0 ). Chemiluminescent emission spectrum (dashed line) from Luminol (10 M) oxidized by under the same aqueous conditions. B. Fluorescence and absorption spectra (full lines) of 3-aminophthalio acid (10 M) in DMSO made basic by the addition of t-BuOH (4%) saturated with t-BuOK (- 10 M). Chemiluminescent emission spectrum (dashed line) from Luminol (10 M) oxidized by oxygen under the same conditions. 

The oxidation of sulfur monoxide with ozone (reaction [V]) is similar to that of nitric oxide (reaction [I]), but it is more exothermic. The chemiluminescence emission spectrum accompanying this reaction extends from about 260 to 480 nm. At least four excited states of sulfur dioxide are thought to be involved A2, and B2, which have radiative lifetimes of 8 ms, 30 ps, 600 ps, and 30 ns, respectively ... 

Fig. 7.23. Comparison of the chemiluminescent emission spectrum of BaO A C = 0 (a) in a crossed beam type experiment, (b) On the surface...

The bioluminescence spectrum of P. stipticus and the fluorescence and chemiluminescence spectra of PM are shown in Fig. 9.7. The fluorescence emission maximum of PM-2 (525 nm) is very close to the bioluminescence emission maximum (530 nm), but the chemiluminescence emission maximum in the presence of a cationic surfactant CTAB (480 nm) differs significantly. However, upon replacing the CTAB with the zwitter-ionic surfactant SB3-12 (3-dodecyldimethylammonio-propanesulfonate), the chemiluminescence spectrum splits into two peaks, 493 nm and 530 nm, of which the latter peak coincides with the emission maximum of the bioluminescence. When PM-1 is heated at 90°C for 3 hr in water containing 10% methanol, about 50% of PM-1 is converted to a new compound that can be isolated by HPLC the chemiluminescence spectrum of this compound in the presence of SB3-12 (curve 5, Fig. 9.7) is practically identical with the bioluminescence spectrum. 

The overall reaction scheme of the luminol chemiluminescence in an aqueous medium is shown in Figure 1. The luminol oxidation leads to the formation of an aminophthalate ion in an excited state, which then emits light on return to the ground state. The quantum yield of the reaction is low ( 0.01) compared with bioluminescence reactions and the emission spectrum shows a maximum1 at 425 nm. 

When acridane 1 is oxidized by dibenzoyl peroxide in propanol/ water in acid or neutral medium, there occurs chemiluminescence whose emission spectrum matches the fluorescence spectrum of acridinium cation (protonated acridine) 2. As radical scavengers have no influence... 

DPA) in dimethylphthalate at about 70°, yields a relatively strong blue Umax =435 nm) chemiluminescence the quantum yield is about 7% that of luminol 64>. The emission spectrum matches that of DPA fluorescence so that the available excitation energy is more than 70 kcal/mole. Energy transfer was observed on other fluorescers, e.g. rubrene and fluorescein. The mechansim of the phthaloyl peroxide/fluorescer chemiluminescence reaction very probably involves radicals. Luminol also chemiluminesces when heated with phthaloyl peroxide but only in the presence of base, which suggests another mechanism. The products of phthaloyl peroxide thermolysis are carbon dioxide, benzoic acid, phthalic anhydride, o-phenyl benzoic acid and some other compounds 65>66>. It is not yet known which of them is the key intermediate which transfers its excitation energy to the fluorescer. 

Chemiluminescence can also be produced in acoustically cavitated alkaline luminol solutions 194>. The emission spectrum is nearly the same... 

When the aldehydes 92 and 95 are treated with oxygen and t-butoxide the emission spectrum of the chemiluminescence matches the fluorescence of a mixture of the acridone and the 9-carboxylate the latter being formed via an acyl anion. 

Chemiluminescence is believed to arise from the 2Bj and the 2B2 electronic states, as discussed above for the reaction of NO with ozone [17]. The primary emission is in a continuum in the range =400-1400 nm, with a maximum at =615 nm at 1 torr. This emission is significantly blue-shifted with respect to chemiluminescence in the NO + 03 reaction (Xmax = 1200 nm), as shown in Figure 2, owing to the greater exothermicity available to excite the N02 product [52], At pressures above approximately 1 torr of 02, the chemiluminescence reaction becomes independent of pressure with a second-order rate coefficient of 6.4 X 10 17 cm3 molec-1 s-1. At lower pressures, however, this rate constant decreases and then levels off at a minimum of 4.2 X 1(T18 cm3 molec-1 s-1 near 1 mtorr, and the emission maximum blue shifts to =560 nm [52], These results are consistent with the above mechanism in which the fractional contribution of (N02 ) to the emission spectrum increases as the pressure is decreased, therefore decreasing the rate at which (N02 ) is deactivated to form N02. Additionally, the radiative lifetime and emission spectrum of excited-state N02 vary with pressure, as discussed above for the NO + 03 reaction [19-22],... 

A more detailed study of the electrochemiluminescence of 9,10-dimethyl-anthracene in dimethylformamide has been carried out by Parker and Short127 who measured the ratio of excimer/molecular fluorescence yields (y°/yp)p in the chemiluminescent spectrum, and (yp/yp)D in the delayed emission spectrum, at different temperatures. The general scheme... 

The most quantitative work was done by Clyne and Thrush.89,106 In their classic studies, they passed an electric discharge through hydrogen in a flow tube, added NO past the discharge, and monitored the chemiluminescence at various points downstream. Their emission spectrum was similar to that of Clement and Ramsay,96 and they confirmed the value of 48.6 kcal/mole for D(H—NO). They further found that In (//[NO]) (/ is the emission intensity) varied linearly with reaction time (distance downstream divided by flow velocity) and with NO concentration as shown in Figures 7-1 and 7-2. Furthermore,... 

An important point is that where it has been measured, the emission spectrum produced by either a chemiluminescent reaction or by triboluminescence is the same as that found in the conventional... 

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