Visible emission

Hahde complexes of Cu with nitrogen base ligands are known to exhibit another form of reversible spectral change known as fluorescence thermochromism. The example of Cu4l4(Py)4 from Table 1 is typical and shows red shifting ia the visible emission spectmm while the sample is both cooled and irradiated with a 364 nm ultraviolet source (7). 

Facility condition/housekeeping (odors, visible emissions)... 

Limitation of visible emission was the origintil form of control of air pollution a century ago. Has this concept outlived its usefulness Discuss this question. 

Historically, the visible emission lines shown in Figure 15-3 were the first atomic hydrogen lines discovered. They were found in the spectrum of the sun by W. H. Wollaston in 1802. In 1862, A. J. Angstrom announced that there must be hydrogen in the solar atmosphere. These lines were detected first because of the lesser experimental difficulties in the visible spectral region. They are called the "Balmer series because J. J. Balmer was able to formulate a simple mathematical relation among the frequencies (in It S). The ultraviolet series shown in Figure 15-3 was... 

The discriminatory emission properties between two-coordinate d ° gold(I) complexes and their respective three-coordinate counterparts have been demonstrated in the literature [6, 10-13]. As discussed in the later sections, Che and coworkers have rationalized that the extraordinarily large Stokes shift of the visible emission of [Au2(diphosphine)2] from the [5da 6pa] transition is due to the exciplex formation ofthe excited state with solvent or counterions [6]. Fackler [14—16] reported the photophysical properties of monomeric [AUL3] complexes, which show visible luminescence with large Stokes shifts (typically lOOOOcm ), suggesting significant excited-state distortion. Gray et al. [10] examined the spectroscopic properties of... 

The [Au2(dcpm)2]X2 complexes (X = C104, PF ", Cp3S03, Au(CN)2 ) display intense photoluminescence with Amax at 360-368 nm in the solid state at room temperature and in glassy solutions at 77 K. Solid samples of [Au2(dcpm)2](C104)2 and [Au2(dcpm)2](PF6)2 individually display a weak visible emission at Xmax= 564 and 505 nm, respectively, but a similar emission is not detected for [Au2(dcpm)2]... 

The Au anion distance of [Au2(dcpm)2][Au(CN)2]2 lies between those with noncoordinating (C104 or PFg ) anions and that of the I salt. The visible emission of the [Au2(dcpm)2] [Au(CN)2]2 solid at 7, = 515 nm is more intense than the visible emission of solid samples of C104 and PF salts of [Au2(dcpm)2] at 564 and 505 nm... 

Draw a picture of the electron jump corresponding to the first line in the visible emission spectrum of hydrogen according to the Bohr theory. 

The yellow flame of traditional oil burners is often surveyed by flame guards that react on the visible emission. More modern oil heaters use blue-burning flames. There, the carbon black of the combustion process is redirected to the combustion area for a more complete combustion, thus giving higher efficiency. With the reduced carbon black their yellow emission in the visible also vanishes, leaving an almost invisible flame, see Fig. 5.44. For these blue flames surveillance based on UV emission is preferable... 

Concentrations of radiolabeled proteins, substrates, or products can be quantified by scintillation counters, which detect both emitters of weak (e. g., 3H) and high energy (e.g., 32P) by excitation of an organic solvent (e.g., toluene) which then emits fluorescence fight. In commercial systems the primary fluorescence is transformed via one or two additional fluorescent dyes in the solution into a visible emission signal which can easily be detected by conventional photomultipliers. 

When the H202-loaded TS-1 sample was irradiated with 355-nm light of a Nd YAG laser or the visible emission of a conventional tungsten source, photodissociation of TiOOH was observed (133). The 837 and 3400 cm-1 bands (and the corresponding 180 substitutes) diminished in intensity (Fig. 20). 

Studies82 of the visible emission from shock-heated CS2 confirm this the temperature dependence of the emission shows that the upper state involved lies ap-... 

This lamp contains xenon at a fairly high pressure and the light is formed via a discharge across a pair of electrodes. A continuous ultraviolet and visible emission is emitted due to the presence of the xenon. In some instruments, the electronic circuitry creates regular pulses of light that are very intense and therefore more useful. This results in a longer life for the lamp. The intensity varies with wavelength. 

One of the major applicahons of pyrolants is to produce smoke clouds or smoke curtains by chemical reactions.I -s] Smoke is defined as condensed particles that can remain in the atmosphere for at least several seconds. The radiative emission from smoke itself is small because of its low-temperature nature. Thus, no visible emission is seen in the dark by the human eye. The applications of smoke are ... 

There are two primary reasons why a fluorescent chemosensor with visible emission would be desirable, in addition to its inherent aesthetic appeal. First, it simplifies qualitative experimental measurement the human eye is sensitive enough to detect extremely small changes in intensity (the limit of visual detection by a dark-adjusted eye has been... 

Reference to Table 8.1 shows that in the absence of chlorine-containing species the visible emission is dominated by BaOH, in spite of the fact that the equilibrium concentration of BaOH is many orders of magnitude smaller than that of BaO. The reason for this is that the hydroxide is formed directly in an excited state in a process known as chemiluminescence, as shown by reaction (8.5) ... 

COMBUSTION About 2500 C to2700 C ++ve Mg(l,g) MgO(s,l) Na(g) 0,0,Hj0,0H CO,COyNj,NO Visible emission zone from Na, Mg, MgO plus continuum radiation from hot particles High temperatures e ite Na atoms to emit at 590nm. Mg droplets move across rone Mg bums rapidly in diffusion flame surrounding liquid droplets... 

The active participation of the So level is indirectly accredited by the simultaneous observation of UV and visible emission in cathodoluminescence... 

Narrow lines at 462, 476, 482, 501 and 590 nm in the luminescence spectrum of the Ca-variety of garnet (grossular) with a relatively short decay time are not typical for traditional trivalent REE in minerals. Evidently they may be connected to visible emission of Nd (Fig. 4.57c,d), but this has to be checked. 

Another group of lines is detected in the titanite luminescence spectrum, which may be considered as connected with the Nd " " emission. Those lines at 589, 658, 743 and 846 nm are especially strong in the luminescence spectra with a narrow gate excited by Aex = 532 nm (Fig. 4.34b). Such a combination of emission lines with relatively short decay times is very unusual for minerals and may not be easily connected to any rare-earth element traditional for luminescence in the visible range. If we were to consider the possible connection with the visible emission of Nd " ", the detected lines correspond very well, for example, to electron transitions from 67/2 level to %/2> fii/2> fi3/2 and Ii5/2 levels. 

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