Triple-triplet

Evidence for photoassociation in the triplet manifold is at present inconclusive. Although Hoytink et al.20 have reported excimer phosphorescence from cooled ethanolic solutions of phenanthrene and naphthalene, concentration and temperature-dependent studies of the emission characteristics must be extended in order to distinguish photoassociation of the triplet state from intersystem crossing of the singlet excimer and possible triple-triplet annihilation. Certainly the decay constant of the molecular triplet state in fluid media is relatively insensitive to solute concentration21 although this... 

On the other hand, the 4.2 K CH2D spectrum shows a triple triplet due to two equivalent atoms and one D atom. The triplet ft/lines due to two H atoms are of equal intensity, 1 1 1, but not a binomial one of 1 2 1. Upon warming above 15 K a new line became visible at the higher field side of each of the central triplet by 0.024 mT and the relative intensity of the new line to the old one reached a limiting value of 1 1 at 40 K. The triplet of CH2D with equal intensity at 4.2 K can be attributed to three totally symmetric A nuclear spin functions (in the C2 symmetry) of two H-atoms which are coupled with the 7 = 0 rotational state [75] ... 

Scheme 7.2 Fluorescence (F) and phosphorescence (P). Normal fluorescence (F) arises from Sj (independently from which singlet has been initially reached, and thus its shape is not affected by the energy of the wavelength used, provided that this has been absorbed. This is the Vavilov rule, rationalized by Kasha as due to the fact that internal conversion among states of the same multiplicity is always the fastest process, see Chap. 3). Delayed fluorescence may involve triple-triplet annihilation, in which self-quenching of the triplet leads back to the singlet Sj, with the usual fluorescence spectrum but the triplet lifetime...

When the kinetics are diffusion controlled an important decrease of the reactivity is observed as the chain length increases. Thus, Horie and Mita, studying the extinction of the phosphorescence of benzyl groups (laser excited) by anthracene rings (triple-triplet absorption), observed that the rate constant k of the reaction between benzyl and anthracene becomes k/2 when anthracene molecules are attached to a polystyrenic chain and when both benzyl and anthracene are attached to... 

Figure 4 (a) ESR spectrum observed at room temperature for a PMMA in benzene solution containing PMNB after 2h ultrasonic irradiation (b) simulated spectrum on the assumption of superposition of a triplet and a triple triplet... 

This ordering by singles, doubles and triples takes added meaning when the failure rates of the active and passive components (Table 1.4.3-1) are included. A doublet has a failure frequency that is the product of the two failure rates a triplet is the product of three... 

Drilling, m. triplet (Mach.) lantern, -salz, n. triple salt. 

Thus the triplet states of the two diastereomers react to yield different product distributions although this effect is far less marked for the triplet than for the singlet reaction, which is essentially stereospecific. The singlet reaction could be either concerted or due to an extremely shortlived biradical. Since the product distributions of the triple reaction of these two diastereomers are different, it is clear that cleavage must occur before complete equilibration. Thus the lifetime of the aliphatic ketone derived biradical must be considerably shorter than the corresponding biradical derived from an aryl ketone. 

The simple 3,4-dihydro-l,2-diazete 1,2-dioxide (1,2-diazetine 1,2-dioxide, DD) system 53 is unknown. 3,3,4,4-Tetramethyl derivative 54 was the first compound of the class to be synthesised [50]. It has an unusually low triplet energy and is a useful triple quencer [51, 52]. Many other derivatives of 53 have recently been prepared in view of their NO-donor properties. 

Triple-layer ODRs, 74 858-859 Triple point of water, 24 439-440 Triple-point temperature, 24 440 Triple porphyrin receptor, 76 787 Triple superphosphate, 77 119-120 Triplet multiplicity, 79 109 Triplet quenching additives, 74 703 Tripodal coelenterands, 24 45... 

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