Platinum spectra

Let us turn to the platinum spectra themselves. Figure 45 consists of three spectra. The top spectrum a shows the platinum signal from an inorganic salt, K2PtCl4. Note the linewidth of 45 Hz, relatively small in comparison with the... 

The Pt NMR parameters of the two published Pts clusters are reported in Table 9 [21] and an example of the complex spectra obtained for such species is presented in Figure 5. In the cluster containing iron, one of the platinum resonances has not been observed because the spectrum width was not large enough to observe the whole spectrum. The relative sign of /( PtA, Pto) can be obtained since the platinum spectrum is of second order. 

Figure A3.10.24 UPS data for CO adsorption on Pd(l 10). (a) Clean surface, (b) CO-dosed surface, (c) Difference spectrum (b-a). This spectrum is representative of molecular CO adsorption on platinum metals [M].

Measurements were performed on a potassium nitrite melt (KNO3) at 450°C. Fig. 73, curve 1 presents the spectrum obtained for a melt layer 0.05-0.1 mm thick, which was placed on a reflective surface (polished platinum). Fig. 73, curve 2 presents the inverted spectrum (relative to curve 1) of a relatively thin layer placed on an absorptive bottom surface (carbon-glass). 

Fig. 1-14. Bragg s resolution of the platinum L spectrum. Each of his peaks contains a series of lines as shown in Fig. —-18. (After Bragg and Bragg, Proc.

Attempts have also been made to obtain the radicals (CF3)3C and CeFs as products of vacuum pyrolysis of (CF3)3CI and CeFsI (Butler and Snelson, 1980b). However, only perfluoroisobutene was observed in an IR spectrum of pyrolysis products of (CF3)3CI. Thermolysis of CeFsl led to formation of CF4, CF3 and CF2 as a result of decomposition of the aromatic ring. This behaviour was explained as due to catalytic effects which take place on the platinum reactor surface. 

Figure 5. X-ray absorption spectrum of a silica supported platinum-iridium catalyst at 100 K in the region of the L absorption edges of platinum and iridium. Reproduced with permission from Ref. 13. Copyright 1982, American Institute of Physics.

Dip the platinum loop in the solution and stick it in the flame. The result is a bright yellow glow. The color comes from two yellow emission lines that dominate the spectrum of sodium. The emission lines result from electrons dropping from the 3p to the 3s orbital. The two lines are very close to one another. The difference in energy is due to the slightly different energies of the electrons in the 3p orbital because of their spin. 

Korzeniewski C, Pons S, Schmidt PP, Severson MW. 1986. A theoretical analysis of the vibrational spectrum of carbon monoxide on platinum metal electrodes. J Chem Phys 85 4153-4160. 

For a comparison of experimental Mossbauer isomer shifts, the values have to be referenced to a common standard. According to (4.23), the results of a measurement depend on the type of source material, for example, Co diffused into rhodium, palladium, platinum, or other metals. For Fe Mossbauer spectroscopy, the spectrometer is usually calibrated by using the known absorption spectrum of metallic iron (a-phase). Therefore, Fe isomer shifts are commonly reported relative to the centroid of the magnetically split spectrum of a-iron (Sect. 3.1.3). Conversion factors for sodium nitroprusside dihydrate, Na2[Fe(CN)5N0]-2H20, or sodium ferrocyanide, Na4[Fe(CN)]6, which have also been used as reference materials, are found in Table 3.1. Reference materials for other isotopes are given in Table 1.3 of [18] in Chap. 1. 

Fig. 7.71 Pt(99keV) Mossbauer spectrum of Pt02 taken at 4.2 K with a source of Au in platinum at 4.2 K (from [332])...

Fig. 7.72 Pt (99 keV) Mossbauer spectrum of the one-dimensional conductor K2[Pt(CN)4] Bro.3o 3H20 at 4.2 K (source Au in platinum at 4.2 K). The solid line represents a single Lorentzian line fitted to the measured spectrum. The dashed line represents the best fit using a sum of two Lorentzian lines with an intensity ratio of 85 15 and with the isomer shifts of the spectra of K2[Pt(CN)4]-3H20 and K2[(Pt(CN)4Br2] (from [333])...

To use the DCI probe, 1-2 xL of the sample (in solution) are applied to the probe tip, composed of a small platinum coil, and after the solvent has been allowed to evaporate at room temperature, the probe is inserted into the source. DCI probes have the capability of very fast temperature ramping from 20 to 700 °C over several seconds, in order to volatilise the sample before it thermally decomposes. With slower temperature gradients, samples containing a mixture of components can be fractionally desorbed. The temperature ramp can be reproduced accurately. It is important to use as volatile a solvent as possible, so as to minimise the time required to wait for solvent evaporation, which leaves a thin layer of sample covering the coil. The observed spectrum is likely to be the superposition of various phenomena evaporation of the sample with rapid ionisation direct ionisation on the filament surface direct desorption of ions and, at higher temperature, pyrolysis followed by ionisation. 

Adsorbed carbon monoxide on platinum formed at 455 mV in H2S04 presents a thermal desorption spectrum as shown in Fig. 2.4b. As in the case of CO adsorption from the gas phase, the desorption curve for m/e = 28 exhibits two peaks, one near 450 K for the weakly adsorbed CO and the other at 530 K for the strongly adsorbed CO species. The H2 signal remains at the ground level. A slight increase in C02 concentration compared to the blank is observed, which could be due to a surface reaction with ions of the electrolyte. Small amounts of S02 (m/e = 64) are also observed. 

In Fig. 2.12 characteristic IR reflectance spectra of concentrated (3 M) methanol on platinum at potentials between 0.45 V and 1.3 V are shown. The single beam spectrum at 0 mV was taken as background. The following characteristic bands allow the identification of bulk products ... 

Fig.45a-c Platinum-195 spectra, 64.52 MHz.aK2PtCl4inD20,bandcds[Pt(NH3)2(l-methylura-cil-N3)]. Spectrum b was recorded using a normal pulse sequence, with 90° pulses. Spectra a and c were recorded using the ARING pulse sequence for removing acoustic ringing... 

Henglein A, Ershov BG, Malow M (1995) Absorption spectrum and some chemical reactions of colloidal platinum in aqueous solution. J Phys Chem 99 14129-14136... 

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