Reflection spectrum Solutions

A = solution absorption spectrum B = diffuse reflectance spectrum C = crystal transmission spectrum D = transmission spectrum as KC1 pellet E = absorption spectrum of melt at 400 °C maximum extinction coefficient in parentheses following the band maxima. 

The normalized absorption and fluorescence spectra of Dye 1 on 200 nm AgBr are shown in Fig. 3. The absorbance was calculated from the measured reflection spectrum using the Kubelka-Munk equation. The absorption spectrum of Dye 1 in methanol solution is also given. The absorption spectrum of Dye 1 on AgBr crystals shows a typical J-aggregate character and gives a sharp and red-shifted band relative to the monomeric band. 

Figure 13.5 Potential modulated reflectance spectrum of p-aminonitrobenzene (PANB) on platinum (solution phase 0.5 mM Na2S04 + 0.05 mM PANB). Applied dc 0.44 V vs. SHE. Modulation amplitude 50 mV. Modulation frequency 33 Hz. Incidence angle 65°. 11 signifies incident polarization parallel to incident plane and perpendicular to electrode surface. J signifies incident polarization perpendicular to incident plane (hence parallel to electrode surface). [From Ref. 50.]...

The interaction between these films and bulk epoxy resin was assessed by immersing an aluminum mirror coated with an air-dried primer film in a Petri dish filled with the epoxy resin, heating the dish in an oven at 100°C for 1 h, allowing the dish to cool overnight, and then extracting any unreacted material from the surface of the mirror by MEK extraction. Figure 6A is the reflection spectrum of a relatively thick film (ca. 3 / n) of neat DGEBA resin (cast onto polished aluminum from a 3% solution in toluene), and Fig. 6B shows the RAIR spectrum obtained from the mirror that was primed, heated in resin, and extracted. The... 

Figure 4. Reflection spectrum of an oxidized copper film exposed to 0.010M acetic acid in ethanol. The dashed line is the spectrum after a 4-h exposure of a fresh substrate to the acetic acid solution. Also shown are the IR peak positions from the gas-phase exposure spectrum (1).

Routine measurements of d-d spectra are performed on solutions. If a suitable solvent cannot be found for a solid sample, a diffuse reflectance spectrum of a powdered sample can be taken. This is actually an absorption spectrum of the surface layers of the sample and is subject to a number of anomalies and artefacts. It is much better to study microscopic single crystals, preferably at low temperatures. Large crystals (if they can be grown) tend to absorb too strongly around band maxima small, thin (c. 0.01mm) plates are best. It is usually necessary to condense the incident beam by means of a lens in order to obtain detectable intensities of transmitted radiation. Thus the technique is more difficult and time-consuming than the familiar, routine solution measurement but it can provide much more information. 

Upon air drying of aminosilane modified silica, samples often get a bright yellow colour. This was also observed upon drying of aqueous APTS solutions. Naviroj et al.12 intended to use FTIR spectroscopy to study the aminosilane structure in aqueous solution at various pH. For spectroscopic analysis, hydrolyzed APTS was casted onto an AgBr plate, dried and analyzed. The spectrum showed varying features according to the drying atmosphere. The spectra did therefore not reflect the solute conformation, but the structure of the dried material. 

Ligand abbreviations in text. 11 Diffuse reflectance spectrum. In MeCN solution. dIn CHC1 solution. In CC14 solution. 

There are a number of examples of monovalence salts, the spectra of which are very closely related to that of the solution dimer for example, K-TCNQ, tetramethyl-p-phenylenediamine (TMPD)-C104, K-chloranil, and cation-radical salts of TTF. The powder absorption spectrum for TTF-C1 is shown by the dashed line in Fig. 5, where it is compared with the spectrum of the solution (TTF+)2 dimer [35]. Analyzing the reflectivity spectrum for light polarized parallel and perpendicular to the c axis, one... 

Figure 12 (a) Optical absorption of trans-PA and a related oligomer. Solid lines polarized absorptions of an oriented PA film (precursor route), calculated from the reflection spectrum (from Ref. 113). The polymer chains are parallel to c. Dashed line absorption of the hexamer all-trans dodecahexaene, in solution in hexane (from Ref. 114). Dotted line hexamer emission in hexane, (b) Optical absorption and reflectivity of unoriented cis- and trans- A films (Shirakawa type) (from Ref. 116). 

A discrepancy between solution-state IR results and theoretical data for the H30+-18-crown-6 complex has been noted <2004JPCA907>. The calculations and solid-state IR data reported in this work agree with previously published work suggesting three linear O- H bonds (structure A). It was concluded from an analysis of the IR spectrum that a structure of the type shown in B reflects the solution situation. Wipff and co-workers refuted <2004JPCA11463> the previous IR analysis, concluding that structure A was correct. This agrees with solid-state IR data for the crystalline complex and with computational results at various ab initio and DFT levels. 

The diffuse reflection spectrum of powdered a-cinnamic acid 1 reflects its solid-state absorption spectrum, which extends into the visible, in contrast to the solution spectrum (Fig. 2.1.2) [20]. It also indicates the wavelength range in the irradiations (365 and 405 nm) and helps in the judgment of light penetration when compared with the absorptivity in methanol (the molecules under (010) of the single crystal are inclined by 32°). 

Since the insolubility of the solid polymer precluded any ultraviolet studies in solution, attempts were made to obtain a diffuse reflectance spectrum of the solid. Meaningful data could not be obtained. Again, however, the liquid polymer could be compared with authentic polystyrene. Figure 4 shows the ultraviolet spectra of the two materials. Although the resolution is poor for the liquid polymer, its spectrum generally agrees with that of polystyrene. 

Fig. 25. Spectrum of triphenylchloromethane -O-O-O" adsorption spectrum in sulfuric acid solution reflectance spectrum of triphenylchloromethane ad-...

Ligand abbreviations in text. Diffuse reflectance spectrum. °Tn MeCN solution. In CHCI3... 

---