Band spike

Here we comment on the shape of certain spin-forbidden bands. Though not strictly part of the intensity story being discussed in this chapter, an understanding of so-called spin-flip transitions depends upon a perusal of correlation diagrams as did our discussion of two-electron jumps. A typical example of a spin-flip transition is shown inFig. 4-7. Unless totally obscured by a spin-allowed band, the spectra of octahedral nickel (ii) complexes display a relatively sharp spike around 13,000 cmThe spike corresponds to a spin-forbidden transition and, on comparing band areas, is not of unusual intensity for such a transition. It is so noticeable because it is so narrow - say 100 cm wide. It is broad compared with the 1-2 cm of free-ion line spectra but very narrow compared with the 2000-3000 cm of spin-allowed crystal-field bands. 

Equations (3.38) and (3.48) are the analytical expressions for the band and adstate contributions to the total reduced-energy spectrum of the adatom DOS, pa(x), respectively. Their graphs are displayed in Fig. 3.4 for 2/3 = 1 and the parameter values indicated. As can be seen, the presence of the large adstate spike at X = Xa markedly reduces the area under the in-band portion of the DOS, in accordance with the sum rule (cf. (3.34))... 

An experimental measurement of the band lineup between the CdS and solar-grade polycrystalline CIGS has been made using contact potential difference (Kelvin probe) measurements in air [10]. This lineup is shown in Figure 9.3. In particular, it shows that no spike was found in the conduction band. The presence of such a spike (believed to occur from previous studies either on single crystals... 

In the spike, GA3 was eluted throughout fractions 10 to 19, but was predominantly located in fractions 10 to 14. Its recovery was confirmed by chromatographing a 1% portion of the 11 to 14 fraction in tne capryl system (Rf 0.88 relative to 0.85 for standard). A number of additional bands are seen, presumably due to the concentration and resolution of trace degradation products from the large amount of GA3 used in the spike. Only one band is found for the natural extract, in the range to be expected for GA3. It occurs in a somewhat later fraction compared to the spike, but this is not unusual in the face of a hundredfold GA3 concentration difference between the two extracts. 

High-resolution agarose gel electrophoresis of serum proteins can reveal the presence of a monoclonal immunoglobulin. The M band in the form of a tall, narrow spike and an intensely stained band can be found anywhere in the gamma,... 

For comparison, the frequency response of a two-port SAW resonator is shown in Figure 6.11 (page 364). Note that it resembles the response of the delay line, with the addition of a sharp spike, where the insertion loss is considerably lower, at the center of the pass band. The similarity of the delay line and resonator frequency responses is a consequence of both devices using the same transducer pattern, while the spiked region of much lower insertion loss is a result of the ridge-reflector array utilized to set up a standing wave. Unlike the highest point of the delay-line spectrum, there is no 6-dB theoretical insertion loss limit for the peak of the resonator spectrum — loss can approach 0 dB. 

Figure 6.11 Frequency response of a SAW resonator, [after Ref. 2] the spike in the center of the pass band is the point of resonance.

According to the results obtained already at 3 percent H spikes and dips occur in the density of states curve of the mixed system. At larger concentrations of impurities due to clustering effect of the impurity, a part of the gaps disappear (16). Finally, it should be mentioned that with the increase of the impurity concentration, as the calculations show, the density of states at the Fermi level increases and therefore we would expect an increase of the transition temperature between the superconducting and normal states. (This experiment, as far as we know, has not been performed yet). We can conclude from this CPA calculation that aperiodicity (disorder) has a rather serious effect on the band structure of polymers. 

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