Four spectra

Fig. 3. Rapid Mo(V) EPR signals obtained on reducing xanthine oxidase at pH 10 with 15 moles of xanthine for 1 min. at about 20 °. The upper four spectra are at 9.1 GHz and the lower four at 34.4 GHz. a, a, c, 8 refer to H2O as solvent and b, b, d, d to D2O. a, b, c, d are computer simulations of the experimental spectra, a, b, c, d, respectively. The interpretation is that two species, each having exchangeable protons which interact with Mo(V), are responsible for the signals. For one of these (dotted complex type II) there are two equivalent interacting protons and for the other (dashed complex type I), two non-equivalent protons. These species are believed to correspond to two different complexes of reduced xanthine oxidase with xanthine. (Reproduced from ref. 78 see also Table 2 for the parameters of the signals.)...

Fig. 10. DLTS spectra for MBE-grown GaAs. The DLTS time constant is r = 8 ms and the filling pulse width 50 ps. The top spectrum is for as-grown material. Lower spectra were taken following hydrogen plasma exposure and subsequent annealing as indicated. A concentration scale applicable to all four spectra is shown in the upper right. (Dautremont-Smith et al.,...

Modem X-ray and y-ray spectrometers frequently employ semiconductor detectors which produce electrical pulses with sizes proportional to the energies of the incident photons. Using a fast ADC, the signal is digitized and a conventional spectrum generated by a dedicated microcomputer. As many as 8K data points (channels) may be sampled with facilities for perhaps four spectra stored in RAM, together with key information such as calibration data, accumulation time, etc. 

What about all the other peaks You can ascribe some sort of meaning to each of them, but it can be very difficult. That s why frequency correlation diagrams, or IR tables, exist (Fig. 120). They identify regions of the IR spectrum where peaks for various functional groups show up. They can get very complicated. Check to see if you can find the C—H stretch and the C—O stretch that are in all four spectra, using the correlation table. It can be fun. 

Using the individual solvents as blanks, acquire a visible absorption spectrum of each sample. Superimpose the four spectra, and determine which solvent is the most effective solvent for extracting chlorophyll from spinach leaves. 

Loss of formaldehyde is not only among the low critical energy processes of oxi-rane and oxetane molecular ions, but also of larger cyclic ethers such as tetrahy-drofurane and tetrahydropyran. [219] Again, imine loss from/V-heterocycles [220] behaves analogously. The mass spectra of tetrahydrofuran, pyrrolidine, tetrahydropyran, and piperidine are compared below (Fig. 6.52). The strong [M-H] peaks in all of those four spectra are due to a-cleavage. 

The four spectra of tetravalent titanium shown in Fig. 21 are closely related. All have a low energy peak at about 5 ev., similar to the characteristic low energy peak in the chromate and permanganate spectra. This peak is also present in the spectra of the other tetravalent titanium compounds, Ti02 and the lactate. In Fig. 21 the principal peak reaches a maximum at about 22 ev. However, it is split and reaches a second maximum... 

When we average n spectra, the signal-to-noise ratio is improved by fn. To improve the signal-to-noise ratio by a factor of 2 requires averaging four spectra. To improve the sig-nal-to-noise ratio by a factor of 10 requires averaging 100 spectra. Spectroscopists record as many as 104 to 105 scans to observe weak signals. It is rarely possible to do better than this because instrumental instabilities cause drift in addition to random noise. 

Figure 8.2.10 (A) Pulse sequence used for selective excitation of each of the four samples in turn. The RF pulses are frequency-selective and applied at different resonant offsets via phase modulation in the time domain. (B) Normal 1H spectrum of (a) the four samples, and the resulting sub-spectra of 0.5 M (b) 1-propanol, (c) 2-propanol, (d) acetic acid and (e) ethanol in D2O. Since the four spectra are acquired within the relaxation time 77 eff, which is typically set to be3Ti, there is an increase in efficiency by a factor of four. Reprinted with permission from Hou, T., Smith, J., MacNamara, E., Macnaughton, M. and Raftery, D., Anal. Chem., 73, 2541-2546 (2001). Copyright (2001) American Chemical Society...

Figure 10. Time - resolved difference spectra from Ca/C EO run at 27 °C. Bottom four spectra expanded 2X relative to top four spectra.

Figure 3-21 Comparison of TCNQ - electronic absorption spectrum and resonance Raman excitation profiles, (a) Electronic absorption spectrum from 15,000 to 17,850 cm-1. The extinction coefficient, e, scale is normalized with respect to e at 663.0nm (15,083cm-1) = 3.0 x 103M-Icm-1. (b) Superposition of the v2 (2,192cm-1). v4 (1,389cm-1), v5 (1,195cm-1) and V9 (336 cm-1) excitation profiles. The relative intensity scale has been scaled to 0.00 to lO.Ofor all four spectra. (Reproduced with permission from Ref. 76. Copyright 1976 American Chemical Society.)...

Then perform PCA on the 4 x 6 matrix consisting of the first four spectra, retaining the first three eigenvalues. 

F ure 9.9. FT-Raman spectra of black electrical tape, 16 cm resolution. Four spectra were acquired successively, each composed of eight scans. Sample heating causes black-body radiation above 2500 cm . Rolloff above 3000 cm is due to detector response. 

Notice that the upper four spectra of Figure 9.4 show a quick disappearance of most of the TOF mass peaks as the delay time was increased from the shortest of 35 gs. The rapid disappearance at longer delay times implies that the neutral products giving the disappearing TOF mass peaks passed the ionization region before the ionizing laser was fired, which, in turn, implies a faster initial velocity of the products when they entered the ionization region. 

These four elementary spectra H (P) are not yet the elementary hydration spectra we are looking for, which correspond to four independent hydration mechanisms. The reason is that the definition of these four elementary spectra only rests on mathematical criteria, and mathematics tells us that instead of taking these four spectra, we may as well have taken any four independent linear combinations of them. We would then have obtained an equally good decomposition of all experimental hydration spectra, with the same statistical errors. 

Fig. 17 Fe L-edge absorption spectra for the compounds Na[Fe(ida)2], K3[Fe(ox)3], [Fe(pha)3] and K3[Fe(cat)3], Inset shows the four spectra shifted in energy to superpose and normalized to the same intensity on the main peak. Altered from [52] with permission, Copyright American Chemical Society, 2010...

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