Spectral broadening, enhanced

Nuclear Overhauser enhancement spectroscopy ( H- H NOESY and NOE) experiments show only the TTC isomer in equilibrium with the TTT isomer for 6,8-dinitro-BIPS [36,55] and 6-nitro,8-bromo-BIPS. The TTC form dominates the equilibrium. Spectral broadening for several proton resonances in the spectra of 6,8-dinitro-BIPS and 6-nitro,8-bromo-BIPS indicate a rapid exchange between these two isomeric forms. The activation energy for this isomerisation is reported to be 43.6 kJ mol and the energy difference between the the TTC and TTT forms is 4.6 kJ mol [55]. 

The enhanced spectral broadening observed in SL s is contained in the final three terms in Eq. (1). The first, ngp, is the spontaneous emission factor and gives the ratio of the rate of spontaneous emission into the laser mode to that of stimulated emission per photon in the mode. In many laser systems ngp is close to unity. However, this is not true of SL s due to the finite population of the lower level of the laser transition. In SL s, ngp approaches unity only at very low temperatures where the carriers are distributed according to Fermi-Dirac statistics. At room temperature ngp 2.5 for (GaAl)As lasers. 

In 1988, the distance dependence of surface-enhanced fluorescence was studied for Langmuir-Blodgett monolayers deposited on silver island films. This study was inspired in part by two earlier reports that examined the distance dependence of SERS of LB films on metal surfaces. Varying numbers of spacer layers of arachidic acid were employed in order to probe the competition between EM enhancement and radiationless energy transfer for a phthalocyanine monolayer. In direct contact with the metal surface, a broadened, enhanced, and red-shifted fluorescence spectrum was observed. These spectral changes can be attributed to a drastic decrease in the fluorescence lifetime of the molecule when it is placed in contact with the metal surface. However, an enhanced version of the unperturbed spectrum was observed when intervening spacer layers were introduced. It was found at enhancements on the order of about 400 could be realized when S monolayers were placed between the Ag island film and the phthalocyanine monolayer. 

Fig. 3.18a-c. Renal artery stenosis, a On color flow sonography, an aliasing phenomenon is present at the proximal portion of the renal artery (arrow). bThe spectral waveform shows an increased peak systolic velocity (2.8 m/s) with spectral broadening. On the intrarenal interlobar arteries, the ascension time is increased at 127 ms. c Gd-enhanced MR angiography confirms the post-ostial renal artery ste-... 

Meier observed that the photoconductivity of )me dyes whidi are already known as efficient carrier generators can be enhanced by doping with electron acceptors (Table 2). He attenpted to apply this effect to the PVK/dye/acceptor system using Methylene Blue and pinacyanol as carrier generators and tetracyano-ethylene as an electron acceptor. Although no substantial increase in photocurrent was observed the spectral responce of the PVK/dye system was broadened to other wavelengths ... 

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