K-emission spectra

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)...

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... 

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) ... 

Figure 8.29(b) shows that an L emission XRF spectrum is much more complex than a K emission spectrum. This is illustrated by the L spectrum of gold in Figure 8.31. Apart from those labelled t and r, the transitions fall into three groups, labelled a, (3 and y, the most intense within each group being a, (5, and y1 respectively.

The vibrational satellites in the 20 K emission spectrum are observed as vibrational doublets, which exhibit the same energy separation of 9 cm" as the two electronic origins II and III. Thus, the same vibrational mode is active in the radiative process of both electronic states II and III. In Fig. 14, only satellites of origin II (at 17,163 cm" ) are specified. 

The 20 K emission spectrum shown in Fig. 14 exhibits vibrational satellites due to activity of fundamentals (e.g. 190, 383, 458, 718, 1400,1484 cm", etc.), of combinations of these fundamentals (e.g. (190 -l- 1484), (383 -l- 1400), (458 -l-1484), (718 + 1400), (718 -I- 1484) cm", etc.), and for the most intense satellites, one observes also the second members of progressions (e.g. 1 x 718 cm, 2 X 718 cm 1 X 1484 cm, 2 X 1484 cm ). These results can be rationalized well, when all vibrational satellites with significant intensity are assigned to correspond to totally symmetric fundamentals. This assignment is also in accordance with the observation that the same fundamentals are built upon the false origins occurring in the 1.3 K emission spectrum. (Fig. 13) An assignment to an alternative symmetry would not allow us to explain the very distinct differences of vibrational activities found in the emission of the states I and II, respectively. 

The fast and non-delayed emission spectrum (Fig. 22 a) shows nearly the same structure as the time-integrated spectrum measured at T = 20 K. (Fig. 14) However, the satellites that result from state III (9 cm higher lying peaks of the doublet structure in the 20 K emission spectrum) do not occur in the fast spectrum. Obviously, at T = 1.3 K, an emission of state III is not observed. This is due to the very fast sir processes to the lower lying triplet substates II and I. (Compare also Sect. 4.2.9.) Thus, the fast spectrum represents the non-thermalized emission spectrum of state II. The Boltzmann distribution does not apply immediately after the excitation pulse, since the thermal equilibration is relatively slow. (For details see Refs. [22,24].) This state II emission spectrum is assigned... 

In conclusion, it is possible for Pt(2-thpy)2, to separate the emission spectra that are super-imposed in time-integrated spectra by time-resolved emission spectroscopy. It is important that one also obtains a low-temperature (1.3 K) emission spectrum from a higher lying state with the corresponding high spectral resolution. This possibility is a consequence of the relatively slow spin-lattice relaxation. Or vice versa, since the monitored time-resolved emission spectra are clearly assignable to different triplet substates, these results nicely support the concept of a slow spin-lattice relaxation as developed above. Moreover, the results presented reveal even more distinctly a triplet substate selectivity with... 

Figure 25 compares the 1.3 K emission spectrum of perprotonated Pt(2-thpy)2 to that of the perdeuterated compound. The assignment of the spectrum of Pt(2-thpy-dg) follows that presented for Pt(2-thpy-hg)2. (See Sects. 4.2.1 and 4.2.4.) Both electronic origins I and II of Pt(2-thpy-dg)2 are blue shifted by (36 1) cm (see also Fig. 26). The same value is also found for origin III [23], showing that the relative splittings, i. e. the zero-field splittings, are maintained. Interestingly,...

The complete description of the different radiations that comprise the Ka emission is complex. In the case of copper, for example, at least 6 different peaks are observed [DEU 95 DEU 96 DIA 00], However, the K emission spectrum can be considered in a first approximation to be comprised of 2 main peaks, Kai and Kc(2. These two contributions cannot be separated by an absorption filter, which is why the resulting beam remains bichromatic. The two peaks can only be separated with the use of a monochromator crystal, under certain conditions. 

Fig. 19 First four groups of bands in the 252.7-nm excited 10 K emission spectrum of Cs2NaY0.99Pr0.oiCl6. The progressions in Vi and in the lattice mode are indicated. Zero-phonon lines are assigned to terminal SLJ states, and the electronic transitions are indicated by horizontal bars above the spectra. The inset shows the first (circled) group of bands in greater detail, with the displacements from the r iu r4g origin marked. (Adapted from [206])...

Figure 8.1 The K emission spectrum of tin. (Reprinted from Ref. 1 with permission.)...

The 77 K absorption spectrum (a) and the 4th derivative (b) of the purified PSII reaction center complex prepared by isoelectric focusing in digitonin solution are shown in Fig. 2. The spectrum is well-resolved than in Triton preparation (1). Absorption in the red maximum region, as well as the peaks around 600 nm, is clearly separated into two components 670 and 680 nm in the red, which might be attributed to the accessory chlorophyll and P-680 plus pheophytin acceptor, respectively. The 77 K emission spectrum of Triton preparation (1) exhibits shoulders on both sides of the main peak at about 681 nm, originating from free chlorophyll and the aggregates. However, the contribution of these components was markedly reduced in the spectrum of the complex prepared by the present procedure a sharp emission peak at about 683 nm was observed in this case. 

Luminescence of Pb + in synthetic alkaline earth sulfates is well known (Folkerts et al. 1995). In this study, CaS04 Pb shows an emission band with a maximum at 235 nm at 300 K, while the excitation maximum is at 220 nm. The decay curve of the emission is single exponential with decay time of 570 ps at 4.2 K. Emission spectrum of BaS04 Pb + demonstrates a broad band peaking at 340 nm with excitation maximum at 220 nm, while in SrS04 Pb + the luminescence band has a maximum at 380 nm. In natural barite and anhydrite samples we detected several narrow UV bands, which may be connected with Pb emission, but for confident conclusion additional study is needed. At any case, Pb + participation in natural sulfates luminescence has to be taken into consideration. 

Fig.5.7. The carbon K emission spectrum from the CO2 molecule. To the left the photographic plate and a corresponding densitometer trace are shown. Calculated spectra are shown to the right, illustrating the sensitivity of the spectrum to the C-O bond length [5.8]...

Fig. 1 curve a shows that at 4.2 K singlet energy transfer from Chi b to Chi a is still efficient as Chi b emission at 657 nm is low. The Chi a emission band is heterogeneous with a maximum at 678-680 nm and a district shoulder at 686 nm. Curves b and c show the 293 K emission spectrum of native and partially denatured Chi a/b-protein 2 respectively (the curves are normalized), a shift from 686 nm to 680 nm being observed. 

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