K emission

Figure 8.29 X-ray fluorescence transitions forming (a) a K emission spectrum and (b) an L emission spectrum. The energy levels are not drawn to scale...

Figure 8.30 K emission spectrum of tin. The ] and P2 lines are at 0.491 A and 0.426 A, respectively. (Reproduced, with permission, from Jenkins, R., An Introduction to X-ray Spectrometry, p. 22, Hey den, London, 1976)...

There are two further effects on K emission XRF which become more important with decreasing nuclear charge. One is the appearance of weak satellite transitions, to lower wavelengths of the main transitions, occurring in the small proportion of doubly ionized atoms which may be produced by the initial X-ray bombardment. The other is a tendency for some transitions to be broadened into bands, rather than the usual sharp lines, due to the... 

Figure 8.29(b) shows that an L emission XRF spectmm is much more complex than a K emission spectmm. This is illustrated by the L spectmm of gold in Figure 8.31. Apart from those labelled I and p, the transitions fall into three groups, labelled a, p and y, the most intense within each group being Mj, Pi and Yi, respectively.

Figure 5.2 Temperature-dependent emission spectra of [(TPA) AuClj (a) 78 K (b) 200 K (c) 250 K. Emission is quenched at room temperature. The excitation spectrum was recorded at 78 K. Reproduced with permission from [22]. Copyright (1995) American Chemical Society.

The gold(III) complexes, ]Au(C N C)L ]" and [Au2(C N C)2(P P)[(C104)2 are emissive in acetonitrile at low temperature. The frozen-state (77 K) emission spectra of the mononuclear complexes [Au(C N C )L [" show well-resolved vibronic structures with spacings in the 1100-1300 cm range, which correlate with the skeletal vibrational frequency of the tridentate C N C ligand. By comparing the emission... 

The excited state redox potential of a sensitizer plays an important process. An approximate value of the excited state redox potential potentials of the ground state couples and the zero-zero excitation Equations (13) and (14). The zero-zero energy can be obtained from of the sensitizer 38 role in the electron transfer can be extracted from the energy (E0 0) according to the 77 K emission spectrum... 

The x-ray emissions are categorized as K, L, M, etc., emissions and as alpha (a) and beta (/3) emissions. It is a K emission if the electron drops from any higher level to the K shell. It is an L emission if it drops from any higher level to the L shell, etc. The a emissions are those that involve electrons that drop just one principle level, such as from the L shell to the K shell (Ka emissions) or from the M shell to the L shell (La emissions). The /3 emissions are those in which electrons drop two levels, such as from the... 

A host material is activated with a certain concentration of Ti + ions. The Huang-Rhys parameter for the absorption band of these ions is 5 = 3 and the electronic levels couple with phonons of 150 cm . (a) If the zero-phonon line is at 522 nm, display the 0 K absorption spectrum (optical density versus wavelength) for a sample with an optical density of 0.3 at this wavelength, (b) If this sample is illuminated with the 514 nm line of a 1 mW Ar+ CW laser, estimate the laser power after the beam has crossed the sample, (c) Determine the peak wavelength of the 0 K emission spectrum, (d) If the quantum efficiency is 0.8, determine the power emitted as spontaneons emission. 

Suppose that a high hydrostatic pressure is applied to the Cr + activated material of the previous exercise, so that the value of DqlB increases up to 2.5. (a) Display the 0 K emission spectrum that you expect to occur, (b) How do you expect that this spectrum will be modified at a room temperature (300 K) ... 

Karlsvik E., Hustad J.E., and Sonju O.K.., Emissions from Wood Stoves and Fireplaces , in Advances in Thermochemica Biomass Conversion 1, ed. Bridgwater A.V., Blackie Academic Professional (London), 690-707 (1993). 

Goodwin, J., Mareckova, K., Emissions of Atmospheric Pollutants in Europe, 1990-99, Topic report 5/2002, EEA, Copenhagen (2002)... 

How would emission intensity be affected by a 10 K rise in temperature In Figure 21-14, absorption arises from ground-state atoms, but emission arises from excited-state atoms. Emission intensity is proportional to the population of the excited state. Became the excited-state population changes by 4% when the temperature rises 10 K, emission intensity rises by 4%. It is critical in atomic emission spectroscopy that the flame be very stable or emission intensity will vary significantly. In atomic absorption spectroscopy, temperature variation is important but not as critical. 

As the removal of a proton from thymine results in the establishment of a tautomeric equilibrium between its two monoanionic forms,3425 the emission spectrum of singly ionized thymine may consist of overlapping spectra of both monoanions. In fact, Gill344 has observed some inconsistencies between the absorption and the fluorescence excitation spectra of thymine in 0.01 N NaOH at room temperature. These inconsistencies were of the same kind as those found later by Berens and Wierzchowski,345 who suggested that at room temperature only the thymine monoanion tautomer (34) fluoresced, while at 77°K emissions of both monoanionic species contributed to the observed luminescence spectrum. 

Call H AND K EMISSION IN THE SECONDARY COMPONENT OF U CEPHEI Akira Okazaki... 

REACTANT REACT ANT(S) OR k EMISSION STIMULATED EMISSION REFERENCE... 

Figure 1. Energy-level diagram for excimer formation. Symbols represent hv, absorbed photon k emissive rate from the monomer species k, bimolecular rate coefficient for formation of the pyrene excimer k, unimolecular rate coefficient for dissociation of the excimer and k, emissive rate from the excimer species. Note no ground-state association is indicated.

The first report of luminescence from a ruthenium(II) complex of this type did not involve an aromatic ligand. Krug and Demas used [Ru(bt)3]2+3I) to demonstrate that an aromatic system is not essential for CT luminescence. However, there was no emission at room temperature and even at 77 K emission was weak. Efficiency improves in complexes of the related aromatic heterocycle (ligand 38), which we have observed to be... 

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