Half-band width

IR spectra of starch can be obtained with an IR spectrometer such as a Digilab FTS 7000 spectrometer, Digilab USA, Randolph, MA, equipped with a thermoelectrically cooled deuterated tri-glycine sulfate (DTGS) detector using an attenuated total reflectance (ATR) accessory at a resolution of 4 cm by 128 scans. Spectra are baseline-corrected, and then deconvoluted between wavenumbers 1200 to 800 cm . A half-band width of 15 cm and a resolution enhancement factor of 1.5 with Bessel apodization are employed. Intensity measurements are performed on the deconvoluted spectra by recording the height of the absorbance bands from the baseline. 

From an NMR perspective, Zn (the only NMR-active zinc isotope) is among a number of potentially important but insensitive metal nuclei such as Ca and Mg. However, Zn NMR spectra of aqueous Zn+ are different from Ca and Mg NMR spectra of aqueous Ca + and Mg + in some respects. For example, Zn NMR spectra of aqueous Zn + have marked concentration dependences in terms of the half-band widths (Avi/2) compared with those of Ca and Mg NMR spectra of aqueous Ca and Mg . 

Although oscillator strength is proportional to the integrated intensity of absorption J rfv, there is often a fairly good correlation between / and emax, the molar absorption coefficient at the band maximum. This correlation is valid if we assume a Lorenzian shape for the absorption band and replace the integral by max A v, where Av is the half-band-width of the absorption band (Figure 3.5b). The half-band-width is defined as the width of the absorption band (in cm-1) where the value of Hence... 

Equipment. The spectra were recorded on a Beckman IR12 spectrometer in the absorbance mode, with low amplifier gain and slit widths smaller than 1.6 of the half-band width of the OH or OD bands. Under these conditions the apparent optical density of the OH bands could be reproduced within 0.5%. To avoid errors from sample emission at temperatures higher than 100°C, the spectra were scanned with the chopper between sample and detector disconnected. 

Fig.6. Changes in half-band width of the v.p band with adsorption and desorption. Open and solid symbols denote adsorption and desorption, respectively.

The correlation between the half-band width (half width at half-maximum heights) of the v/p band and PIP, were plotted in Fig. 6. Here, the half-band width of the band of the bulk liquid is shown by the horizontal line. The half-band width varies from 2.8 to 3.5 cm 1. 

The half-band width is constant below PIP, = 0.37, and then suddenly drops with the increase of P/P,. The relationship between the half-band width and PIP, has a clear hysteresis corresponding to that of adsorption isotherm. The half-band width upon desorption is smaller than that upon adsorption. 

The relaxation time upon desorption is greater than that upon adsorption at the same PIP, in the hysteresis region. This distinct difference provides an important information. The half-band width is almost constant from P/P = 0.70 to P/P = 0.59 on the course of the desorption and then it increases gradually with the decrease of P/P . Consequently, the... 

H-abstraction intramolecular, 378 Half-value concentration, 181 Half-band width, 69 Half quenching concentration, 173 Hamiltonian operator, 65 perturbing, 67 Hammet equation, 110 He-Ne laser, 318 Heavy atom perturbation, 70 external, 145 intermolecular, 71 intramolecular, 71... 

Figure 3.5 Absorption curve, (a) Plot of molar extinction coefficient e- vs v (b) J - rfv s eaMX Av, where Av is the half band width.

Pressed pellets of BaTiC>3 were sintered in a platinum dish for six hours at 900°C in a controlled partial pressure of oxygen. The samples were quenched to room temperature, and the spectra recorded on a four-slit double-monochromator Raman spectrophotometer. An Ar+ laser with excitation at 514.5 nm was the source. The spectra were recorded at room temperature. Figure 4-30 shows the spectrum of BaTiC>3 whose Ba/Ti ratio is equal to 0.9999. The Raman spectrum is sensitive to the Ba/Ti ratio and theoxygen non-stoichiometry. The half-band width is variable as well as the intensity ratio of the 525 and 713 cm-1 bands. The ratio (I525/713) is at a minimum at the composition of 0.9999, and this can be observed in Fig. 4-31, which shows a plot of the intensity ratio (I525//713) vs. the Ba/Ti composition. 

Figure 4-30 A Raman spectrum of BaTi03 for Ba/Ti = 0.9999 with spectral parameters (intensities and half-band width) defined. This sample was quenched after 3 hours in 1 atm oxygen. (Reproduced with permission from Ref. 51.)...

FWHM (Full Width at Half Maximum) See half-(band)width. 

Figure 6.8-15 Calculated intensity ratio for different neighboured maxima in the spectrum of nitrogen. Peak X 826.2 nm Peak Y 828.1 nm Band profile for T = 2000 K using an interference filter with half band width of 0.5 nm.

A number of studies have been made of the solvent dependence of the infrared spectra of carbonyl compounds. The results have shown that to a limited extent this effect can be used to aid assignment of CO-stretching fundamentals. Quantitative measurements of the variations on frequency and half-band widths vn2 with changing solvents have been made, but as yet, the solvent dependence of the intensities has not been studied in detail. 

Half-band widths vii have also been used as a measure of the solvent dependence of a CO-stretching fundamental and correlations similar to those noted for frequency shifts with changing solvent were observed. Thus, it has been established that, as the polarity of the solvent increases, the half-band widths of a CO-stretching mode also increase (45). Furthermore, a plot of the half-band width of the 62 band against that of the e band for the compound Mn2(CO)io gave a linear relationship for different solvents (259). Similar relationships have been established from the half-band width data for the compounds Ni(CO)4 and Co(CO)3(NO) in different solvents (45). 

One more point should be brought out at this time all of the observed bands are sharp, their position is constant, and their half-band widths are approximately equal for all of the oils indicating that there is little change in the average olefin type represented by each band in the three oils. A more detailed discussion of the IR characteristics of olefins may be found in the book by Bellamy (14) and the work by McMurry and Thornton (15). 

In this case, we guess that, it is unlikely that the vibrational relaxation of physisorbed acetonitrile concerned is faster than that of liquid molecule. Above PIP, - 0.30, the half-band widths of the v, p band tend to be narrower than that of bulk liquid (Fig.5). That is, t values are slightly longer than that of the bulk liquid at the same temperature. Accordingly, it is concluded that motion of acetonitrile molecules condensed in mesopores is a little more perturbed than that of bulk liquid. 

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