Eximers

This is an introduction to the techniques used for the calculation of electronic excited states of molecules (sometimes called eximers). Specifically, these are methods for obtaining wave functions for the excited states of a molecule from which energies and other molecular properties can be calculated. These calculations are an important tool for the analysis of spectroscopy, reaction mechanisms, and other excited-state phenomena. 

Bcnzophenon-oxim und Dicyclohexylketon-oxim werden in Bis-[2-methoxy-athyl]-ather bei 105-110°, 1,3-Diphenyl-propanon-(2)-exim in 1,4-Dioxan bei 85-90° durch Diboran zu den Hydroxylaminen reduziert . 

Pyrene fluorophores are also used as probes. Derivatives of pyrene show /.max/ Xem 340/376 nm, e 4.3 x 104 M 1 cm-1, and environmental sensitivity, this fluorophore can be used to report on RNA folding [102]. Pyrene also displays a long-lived excited state (x > 100 ns), which allows for an excited pyrene molecule to associate with a pyrene in the ground state. The resulting eximer exhibits a red-shift in fluorescence intensity (A,em 490 nm). This characteristic can be used to study important biomolecular processes, such as protein conformation [103]. 

C. Theodorakopoulos, The Eximer Laser Ablation of Picture Varnishes, PhD thesis, Royal College of Art, London, 2005. 

Sameshima, T. Usui, S. Sekiya, M. 1986. XeCl eximer laser annealing used in the fabrication of poly-Si TFT s. IEEE Electron Dev. Lett. EDL-7 276-278. 

The self-assembly of this fundamental building block of chromatin is a topic of enduring interest. DNase I digestion experiments as well as spectroscopic studies indicate that nucleosome core particles can be reconstituted by salt-jump (i.e., diluting NaCl concentration from 2.0 to 0.2 M) or by direct mixing of histones and DNA at the lower salt concentration. Daban and Cantor used the increase in eximer fluorescence to investigate the reassembly process in terms of a two-state model ... 

THF tetrahydrofuran, NaNap sodium naphthalenide, Na2St disodium stilbene dianion, BP benzoyl peroxide, DME 1,2-dimethoxyethane, TMBD tetramethylbenzidine dication diperchlorate, WBP Wurster s blue perchlorate, LP lauroyl peroxide, FLSPEC fluorescence spectrum obtained, FPSPEC fluorescence and phosphorescence spectrum obtained, FXSPEC fluorescence and eximer spectra obtained, DPAC12 9,10-dichlorO 9,10-dihydro-9,10-diphenylanthracene. 

Nearly all the nonfluorescent emission bands reported in these studies have been found at longer wavelengths than the expected fluorescence. They have been variously ascribed to eximers6,15 or to phosphorescence1315 of the electroactive substance. Some apparently do not arise from the electroactive compound itself.16 On oxidation of the pyrene anion radical with Wurster s blue perchlorate, an emission band was obtained which corresponded closely to the known pyrene eximer emission.15 Several spectra obtained from polycyclic aromatic hydrocarbons by electrochemical treatment at constant applied voltage have... 

Eximer Fluorescence. Since Forster and Kasper discovered concentration-dependent long-wavelength emission resulting from association of an electronically excited pyrene molecule with another ground state pyrene molecule,39 the phenomenon of excimer fluorescence has been studied extensively.40 The mechanism for excimer formation and emission can be represented by... 

Eximer light sources may require water cooling for optimal operation. Their life times have not yet been determined, but excimer lamps (see Table 1) have been operational for more than 3000 hours with radiant efficiencies of approximately 6%. 

Photodimerization of dibenzoazaazulene 10 gave only syn dimers 61 and 62, with 61 favored in solid-phase dimerization and 62 predominating in solution. Eximers have been proposed to be responsible for the formation of syn isomers (84JOC2978). 

The base-base distance along the N-vinyl type polymer chain is, in general, shorter than that of the methacryloyloxy type. For the N-vinyl type polymers an eximer emission as well as a Xmax shift of UV spectra was observed because the distances between the bases are shorter17. These phenomena, however, have never been observed in polyMAOA, polyMAOT and polyMAOU. The UV spectral data for the polymers have almost identical kn,ax values as their model compounds, and less hypo-... 

Praschak D, Bahners T, Bossmann A and Schollmeyer E, Oberflachenmodifizierung von PES durch Bestrahlung mit Eximer-Lampen . Melliand Textilberichte, 1997,78(7/ 8), 531-532. 

Metal atom lasers and eximer lasers for in situ and LIDAR detection... 

Two groups within NASA, one at Goddard Space Flight Center, under the direction of Bill Heaps, and the other at the Jet Propulsion Lab under Laudenslager and McDermid, have respectively developed balloon-borne LIDAR methods for OH and developed eximer laser systems for extending the LIDAR method to lower detection thresholds. This research has important implications for both stratospheric and tropospheric research. Such laser ranging techniques also have important implications for intercomparison studies, particularly with mm-wave and far infrared emission ex periments. 

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