Band red shifted

Their spectral patterns are characterized by the presence of several bands red-shifted relative to the 0 electronic Sj Sq origin of the bare chromophore Cr at 37618 cm (peak B). The most intense one is separated from the peak B of the chromophore by the A values reported in the figure. Since a red-shifted Sj Sq origin denotes an increase of attractive interactions in the complex by the electronic transition, the Av values of Fig. 10b, c, and d, indicate that bond strengthening follows the order [Cr-Mrr] > [C/j-M/js] > [C/j-Mss]. 

Figure 159 EL spectra (a) and EL transients (b) for SL ITO/ Polymer/Metal LEDs (1) ITO/MEH-PPV/A1 (2) ITO/MEH-PPV/ MEH-PPV/(Mg/Ag) (3) ITO/M3EH-PPV/(Mg/Ag). EL spectra are recorded at different voltage pulse amplitudes. Characteristic cathode metal emission lines are indicated along with the position of broad band-red shifted emission maxima from the polymers. For chemical meaning of MEH-PPV and of M3EH-PPV, see Figs. 106 and 108. The transient current under a lps pulse (4) and transient response of EL polymer and cathode metal emission spectral regions at two different pulse amplitudes, 4.3 MV/cm (5) and 6.6MV/cm (6) have been measured on ITO/MEH-PPV/A1 device. EL transient are normalized to the maximum intensity of the polymer emission. After Ref. [472]. Copyright 2000 American Institute of Physics.

In the bulk, the low concentration of ground-state pairs excludes their observation by absorption. The formation of the excited-state complex, termed exciplex, is a collisional process electronic excitation of either the acceptor or the donor leads to the formation of a locally excited state (for instance, in hydrocarbon molecules, it is a nn state). During the lifetime of this state, a collision with the other partner (which is in the ground state) leads to the formation of the exciplex. This mechanism is compatible with the fact that the absorption and fluorescence excitation spectra of the system are identical with those obtained by superimposing the spectra of the individual components. At the same time, the fluorescence emission spectrum changes drastically—a broad band, red shifted with respect to the bare molecule s emission spectrum, appears. It is usually devoid of vibrational structure, and is shifted to longer wavelengths as the solvent polarity increases [1],... 

Intramolecular Excimer Fluorescence Studies in Polymers Carrying Aromatic Side Chains. Some years ago, it was shown that certain excited aromatic molecules may form a complex with a similar molecule in the ground state, which is characterized by a structureless emission band red-shifted relative to the emission spectrum of the monomer. The formation of such complexes, called "exclmers", requires the two chromophores to lie almost parallel to one another at a distance not exceeding about 3.5A° (11). Later, it was found that Intramolecular excimer formation is also possible. In a series of compounds of the type C5H (CH2)jiC H5, excimer fluorescence, with a maximum at 340nm, was observed only for n 3 -all the other compounds had emission spectra similar to toluene, with a maximum at about 280nm (12). Similar behavior was observed in polystyrene solutions, where the phenyl groups are also separated from one another by three carbon atoms (13). 

For both PF2/6 and PF8 the aforementioned main chain characteristics are essentially identical and so any pronounced differences are likely to originate in secondary structural characteristics of the functionalizing side chains. PF8 studies by Bradley and coworkers [16] first identified the unusual spectroscopic emission band now conventionally referred to as the phase . The hallmark signature of this peculiar chain structure is a relatively sharp series of emission bands red shifted some lOOmeV from those seen when the polymer is prepared in a glassy state, tt-Conjugated polymers have strong electron-phonon coupling and so, in addition to the it-it emission, there is a manifold of vibronic overtones spaced approximately 180 meV apart and red-shifted from the dominant n-n emission band. 

The existence of different chlorophyll forms in vivo can best be seen by comparing the absorption spectrum of pure chlorophyll a in ether with the spectra of two algae that are known from column separation work to contain Chi a only. As many studies had already shown that both the band shapes and peak positions of in vivo Chi a varied in the many algae and plants that had been examined, it is not surprising that the in vivo absorption spectra of Cryptomonas and Botryoglossum, seen in Fig. 6 (A), had the absorption band red-shifted from solution spectra, but the spectra also indicated the presence of Chi a in different forms in the two algae. 

NLO properties. For different polyene series (Figure 1.13), the MLCT bands unexpectedly blue-shift as the number of ethylene units increases from one to three, and / o maximises at = 2. This behaviour is in marked contrast with known push-pull polyene organic chromophores, in which the tt-tt intramolecular charge transfer (ICT) bands red-shift as the number of ethylene units increases and the values increase steadily with Time-dependent (TD)-DFT calculations corroborate the... 

Fusion of a pyranone ring across the /i-face (7,8-bond) of 2,2-diphenylbenzopyran, achieved by propargylation of 5-hydroxycoumarin, modifies the photochromic properties relative to the corresponding 2//-naphtho[l,2-()]pyran. The absorption bands, red shifted to 420 and 512 nm from 403 and 481 nm, are of lower intensity and bleaching to the closed form is significantly faster <02HCA442>. 

When incubated with the sodium salt of CoM, the d-d electronic bands red shift by... 

---