Emission dimole

There is a significant, although low, probability that two excited singlet oxygen molecules can collide. Such collisions appear to lead to emission ( dimol emission) resulting from the simultaneous loss of... 

The maximum of emission from excited triplet carbonyls occurs at 460 nm while that from singlet oxygen at 634 nm (dimol emission) and 1,270 nm (monomol emission) [19]. 

Emission from dimols of singlet oxygen may be detected by photomultipliers used for measurement of chemiluminescence from hydrocarbon polymers with a maximum spectral sensitivity at 460 nm. The above scheme, however, requires the presence of at least one molecule of hydrogen peroxide in close vicinity to the two recombining peroxyl radicals and assumes a large heterogeneity of the oxidation process. 

The occurrence of the dimol emission from two O A,) molecules, described in Section II-B, suggests that it may be possible to follow the concentration of 02(1AS) in a reaction system by observation of the emission at 6340 or 7030 A. In view of the difficulty of finding detectors of high sensitivity for 1.27 [x, this course has much to commend it, although it is essential that the kinetic order in [02(1AS)] of the dimol emission be established, and that, for absolute determinations, the absolute rate constant of the reaction... 

Arnold et al.23 mention that they observe very weak dimol emission at A = 6340 A from reaction (15b) (and from the similar reaction of atomic oxygen with nitrogen dioxide... 

Several curious results emerged in subsequent studies. Bader and Ogryzlo22 found that addition of ozone to a discharge-excited 02 stream, from which atomic oxygen had been removed by HgO, lowered [02(1E ,+)] by more than a factor of 10, and led to the formation of atomic oxygen. On the other hand, the intensity of the dimol emission bands at A = 6340 A and A = 7030 A increased on addition of ozone, and it was suggested that [02(1A5)] was actually increased by the reaction... 

This conclusion is borne out by kinetic evidence which shows that the intensity of emission is proportional to [02(1A9)]3. Since [02(1H9+)] oc [Oz(1A9)]a in the discharge-flow system, the result indicates that [N02 ] oc [02(1A9)][02(1S9+)]. The experimental evidence does not allow description of the detailed mechanism for reaction (32). Two possibilities are (a) that a low-lying excited state of N02 is excited from one or other of the excited 02 species before a second energy-transfer reaction produces the emitting state of N02, or (b) that direct transfer to N02 takes place from an 02(1Afl) 02(1S9+) dimol. Although emission from this latter dimol is not observed in the gas phase, since [02(1S9+)] is normally very small, it has been seen in condensed phase systems.20... 

Dimole absorption and emission, 247 Dioxetane formation, 253 Donor-acceptor energy levels, 201 property, energies of, 289 Dipole-dipole resonance energy transfer, 192, 193... 

Rate constant for the dimol emission from OjCa A ) measured at 295 K... 

We report here the chemiluminescence of these reactions observed in the visible spectral region (Vis-CL), along with the IR-CL emission of 2. A spectral analysis of the emission as well as the influence of the solvent on the Vis-CL intensity revealed that the singlet-oxygen dimol is one of the emitters of the chemiluminescence ... 

The emission at X > 600 nm is assigned to the singlet-oxygen dimol species, which is known to have characteristic bands at X 633 and 703 nm. The CL intensity at X 626 and 700 nm for the reaction of DMD with amines BPP and DAP is more then twice in acetone-deuteroacetone (l.T) and acetone-deuterochloroform(l l) than in pure acetone. Clearly, this increase in the Vis-CL intensity is a consequence of the prolonged 02 lifetime in deuterated solvents. 

We have found that in addition to the IR-CL of 02, reported previously by Lange and Brauer, decomposition of KHSO5 by acetone leads to the Vis-CL emission, whose spectrum consist of two emission bands at X 580-610 nm and 610-645 nm. Furthermore, also the CL at X 700 nm (interference filter) was detected. The emission intensities at X 626 nm and 700 nm is increased more then three times in D2O compared to H2O, which implies that the singlet-oxygen dimol species intervenes. 

Effect of DABCO on the singlet oxygen dimol emission... 

Kazakov DV, Kazakov VP, Maistrenko GYa, Mal zev DV, Schmidt R. On the effect of l,4-diazabicyclo[2.2.2]octane on the singlet-oxygen dimol emission chemical generation of ( 02)2 in peroxide reactions. J Phys Chem A 2007 111 4267-73. 

So far, preassociation and the possibility of photorecombinative laser action have been investigated in the formation of NO 85>83>, n2 85) CN 85>, and the halogens 87>. A somewhat different system is the dimol" emission from an excited-state dimer of molecular oxygen in either the or 1Af state 89>. 

Near-i.r. irradiation has been used to photosensitize the production of singlet oxygen.2720 Dimol emission, 20a(1A ) -> 202(32 ) + hv633, has been observed from neodymium-glass-pumped oxygen in the gas phase and in 1,1,2-trichloro-trifluoroethane solution.2726... 

The data suggest that activated dimol luminescence is a universal phenomenon which can be observed in solvents of widely varying nature and can be surprisingly efficient. This type of sensitized luminescence may account for the wide distribution of red luminescence often attributed to singlet oxygen dimol emission in biological and other systems. 

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