Locally excited state temperature dependence

The scheme invokes the existence of different local environments that can not interconvert on the lifetime of the excited states (M and M ). It is further supposed that all emission in the monomer region is due to one type of localized excited state (M ) whereas excimer formation occurs very rapidly from Deviations in the excitation spectra and excimer decay kinetics are explained by the existence of a subset (D) of Mj responsible for the deviation of 304 nm constituting an excited-state rapid equilibrium between unperturbed (M ) and perturbed (D ) alkylnaphthalene species. The temperature dependence of the decay of monomer emission was rationalized in terms of two excimeric species E and E. At low temperatures, decay from M is biexponential, the longer-living component resulting from dissociation of E whereas the greater complexity of the decay kinetics at higher temperatures is a consequence of the influence of the excimer E. ... 

Atoms and molecules have available to them a number of energy levels associated with the allowed values of the quantum numbers for the energy levels of the atom. As atoms are heated, some will gain sufficient energy either from the absorption of photons or by collisions to populate the levels above the ground state. The partitioning of energy between the levels depends on temperature and the atom is then said to be in local thermal equilibrium with the populations of the excited states and so the local temperature can be measured with this atomic thermometer. 

We used short broadband pump pulses (spectral width 200 cm 1, pulse duration 130 fs FWHM) to excite impulsively the section of the NH absorption spectrum which includes the ffec-exciton peak and the first three satellite peaks [4], The transient absorbance change signal shows pronounced oscillations that persist up to about 15ps and contain two distinct frequency components whose temperature dependence and frequencies match perfectly with two phonon bands in the non-resonant electronic Raman spectrum of ACN [3] (Fig. 2a, b). Therefore the oscillations are assigned to the excitation of phonon wavepackets in the ground state. The corresponding excitation process is only possible if the phonon modes are coupled to the NH mode. Self trapping theory says that these are the phonon modes, which induce the self localization. 

For spectra corresponding to transitions from excited levels, line intensities depend on the mode of production of the spectra, therefore, in such cases the general expressions for moments cannot be found. These moments become purely atomic quantities if the excited states of the electronic configuration considered are equally populated (level populations are proportional to their statistical weights). This is close to physical conditions in high temperature plasmas, in arcs and sparks, also when levels are populated by the cascade of elementary processes or even by one process obeying non-strict selection rules. The distribution of oscillator strengths is also excitation-independent. In all these cases spectral moments become purely atomic quantities. If, for local thermodynamic equilibrium, the Boltzmann factor can be expanded in a series of powers (AE/kT)n (this means the condition AE < kT), then the spectral moments are also expanded in a series of purely atomic moments. 

Intramolecular transfer of excitation is of considerable importance in photochemistry. Leermakers, Byers, Lamola, and Hammond (332) have demonstrated by optical emission the occurrence of intramolecular electronic energy transfer in 4-(l-naphthylalkyl)benzophenone. de-Groot and van der Waals (333) have examined the temperature-dependent ESR spectra of the phosphorescent states of benzene, toluene, triptycene, and tribenzotriptycene. The latter two molecules consist of three benzene or naphthalene systems joined together, and their ESR spectra reveal the intramolecular excitation transfer between the benzene or naphthalene subsystems. At 20°K, the excitation is mainly localized in one of the subsystems, but at such... 

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