Cooperative excitation

The existence of this TTA bimolecular process makes it possible to carry out cooperative excitation of energy rich molecular states by low energy quanta. In particular, formation of upper excited singlet states as a result of TTA has been observed for several aromatic hydrocarbons (1) and metalloporphyrins ( ) by the demonstration of annihiTation-induced delayed fluorescence (AOF) from upper singlet states. 

We have found that emission spectra of the cooperatively excited ADF from upper electronic states and of the one quantum excited PF are different. ADF spectrum is shifted in the longwave direction with respect to PF spectrum (see Table II). The shift effect depends on solvent type. ADF spectral shift is most considerable and comprises 500 cm"l (see Fig. 1) for the case of ZnTPP in decane. 

Thus we may consider that ADF from So states takes place in a dimeric complex which dissociates after deactivation of the cooperatively excited Sg state. 

If we expand Eq. (10-7) and simplify aeeording to the symmetry of the problem, (Richards and Cooper, 1983) the integral breaks up in the way it did for the helium atom excited state... 

Multiphoton processes are also undoubtedly involved in the photodegradation of polymers in intense laser fields, eg, using excimer lasers (13). Moreover, multiphoton excitation during pumping can become a significant loss factor in operation of dye lasers (26,27). The photochemically reactive species may or may not be capable of absorption of the individual photons which cooperate to produce multiphoton excitation, but must be capable of utilising a quantum of energy equal to that of the combined photons. Multiphoton excitation thus may be viewed as an exception to the Bunsen-Roscoe law. 

Ravikanth M, Chandrashekar TK (1995) Nonplanar Porphyrins and Their Biological Relevance Ground and Excited State Dynamics. 82 105-188 Rawle SC, see Cooper SR (1990) 72 1-72 Raymond KN, see Baker EC (1976) 25 21-66... 

The ground state as well as the 6.2 keV excited state of Ta possesses sizeable electric quadrupole and magnetic dipole moments (cf. Table 7.1 at the end of the book) which, in cooperation with the extremely narrow line width, generally yield well-resolved Mossbauer spectra even in cases with relatively weak interactions. 

Photo-excitation and de-excitation are basic processes in nuclear reactions. A Japanese-Hungarian cooperation investigating these processes has yielded good results during the past few years [21-26], These studies used weighable amounts of "Tc to look at the (y, y ) reaction that leads to the production of the nuclear isomer "mTc by electron linear accelerator irradiation. 

The authors express their sincere thanks to their co-workers and colleagues, without whose contributions this article could not have been written their names are cited in the references. Prof. Helmut Werner from Wiitzburg University, in whose Institute the title complex was initially prepared, is very specially thanked for the intense and exciting chemical cooperation for many years. 

Ramakrishna G, Goodson T III, Rogers-Haley JE, Cooper TM, McLean DG, Urbas A (2009) Ultrafast intersystem crossing excited state dynamics of platinum acetylide complexes. J Phys Chem C 113 1060-1066... 

In the same line, [Fe(qsal)2][Ni(dmit)2].2CH3CN has also been proven to show a cooperative spin transition based on n-n interactions between ligands [105]. Moreover, this compound is also one of the rare Fenl complex to exhibit the light-induced excited spin state trapping (LIESST) effect. 

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