Site-selective excitation

PL investigations of site-selective excitation, according to which the films show additional absorptions at lower frequency than those seen in dilute solution [45] ... 

As we will demonstrate, luminescent properties, radiative transition characteristics as well as emission under site selective excitation depend on the local environment s)rmmetry of the luminescent center. Therefore it is necessary to take into account and to describe the different local symmetry. There are two systems commonly used in describing symmetry elements of punctual groups ... 

In all cases the complexes were strongly luminescent at room temperature, in contrast to the precursor homonuclear derivatives, and at an energy that was tunable, displaying a site-selective excitation that depended on the Au Ag molar ratio, lying between the emission bands of the pure Ag and Au compounds. For instance, while the homonuclear derivative La[Ag(CN)2]3 emitted at 77 K at 345 and 470 nm (exc. 310 nm) and the gold complex La[Au (CN)2]3 at 431 and 493 nm (exc 310 nm), the mixed metal systems tended toward Ag or Au peak positions, depending on loading. 

Fig. 24. The RT emission spectra of the core-shell of Eu Y203/Al203 by site-selective excitation at Xexc = (a) 355, (b) 533.55, (c) 525.97, (d) 526.41 nm. The emission was detected using a boxcar integrator that averaged the signal from a cooled PMT with 15 ps gate and 0.3 ms delay from the pump laser pulse (redraw after (Chen, X.Y. et al.,...

Similarly to the situation found for Pt(4,6-dFppy)(acac) in /7-octane, several discrete sites are observed in the nonselectively excited emission spectrum of Ir(4,6-dFppy)2(acac) in CH2C12 at 4.2 K (not shown, but compare [50]). However, for the Ir(III) compound the inhomogeneously broadened background is much more intense. In Fig. 7, site-selectively excited emission spectra at different temperatures and a site-selectively detected excitation spectrum are displayed for the region of the electronic 0-0 transitions of the site of lowest energy, denoted as site A. 

YBOsiEu vary with the synthetic route. The YBOaiEu powder synthesized through a sol-gel method exhibit three Eu sites identified by site selective excitation. The Eu concentration dependence of emission intensity and Eu luminescence decay from 300 to 15 K prove that the energy migration is phononassisted. (Boyer et al., 2003). 

Fig. 3. Emission spectra of Pd(2-thpy)2 (a) in an n-octane Shpol skii matrix (line spectrum) and (b) in butyronitrile (broad band spectrum) at T = 1.3 K, Aexc = 337.1 nm (N2-Laser). The energies of the vibrational satellites are specified relative to the electronic origin at 18,418 cm f The structures marked by asterisks on the high energy side of the electronic origin result from other sites and vanish with a site-selective excitation, e.g. at 19,113 cm (18,418 cm i -1-695 cm vibrational satellite). Concentration of Pd(2-thpy)2 10 mol/1. Note Fora better comparison, the broad band spectrum is shifted by 200 cm to lower energy. (Compare Ref. [56])...

Fig. 27. Emission spectrum of (b) Pt(2-thpy-h6)(2-thpy-d6) at T=1.3 K of site A. For comparison, the spectra of (a) Pt(2-thpy-hg)2 and (c) Pt(2-thpy-d6)2 are also reproduced. (Compare Fig. 25.) The compounds are dissolved in an n-octane matrix (= Shpol skii matrix) with a concentration of c = 10 mol/1. The compounds (a) and (c) are excited at Aexc = 457,9 nm (A 21,839 cm while the partially deuterated compound (b) is site-selectively excited at the elec-...

Figure 2. Illistration of atomic site selective excitation by soft x-ray photons.

The fragmentation of nitrous oxide following site-selective excitation of Is electrons of ah three atoms to the lowest unoccupied molecular orbital clearly shows a dependence on the atomic site of excitation as shown in Fig. 6 and Table V. The fragmentation patterns are not consistent with the idea of a Coulomb explosion as defined in the preceding section, or with the concept of localized bond rupture around the atomic site of excitation. The... 

Laser spectroscopy has been extensively used in solids to suppress inhomogeneous contributions and to isolate features which are characteristic to a designated site or field distribution. In this, site selective excitation spectra (fig. 3) or FLN have been used to deconvolute the individual components of composite spectra. For example, when trivalent rare earths are doped into a divalent host such as... 

Figure 20 Photoluminesoenoe spectra of [Ag(CN)3/KCI] doped crystals at 77 K. The letter assignment of the luminescence bands follows the notation used In Table 2. Reproduoed with permission from Omary MAand Patterson HH (1998) Luminescent homoatomio exciplexes in dicyanoargentate (I) ions doped In alkali halide orystals 1. Exciplex tuning by site-selective excitation. Journal of the American Chemical Society 20 . 7696-7705.

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