Absorption lines, relative intensity

Figure 1-8 shows log-log curves calculated from Barkla s absorption-coefficient data. (A log-log plot shows most clearly what Barkla discovered.) For carbon, the wavelength distribution is virtually unchanged from that of the incident polychromatic beam, mainly scattered x-rays being detected the situation is reminiscent of Figure 1-5. The curve for calcium, on the other hand, begins with a straight line that shows the presence in the scattered beam of a relatively intense component for which k is large and sensibly constant. The curve for tin shows two such components. Barkla realized that these components are emitted, and he eventually called them K and L spectra.22 He...

The method involves the irradiation of a sample with polychromatic X-rays (synchrotron radiation) which inter alia promote electrons from the innermost Is level of the sulfur atom to the lowest unoccupied molecular orbitals. In the present case these are the S-S antibonding ct -MOs. The intensity of the absorption lines resulting from these electronic excitations are proportional to the number of such bonds in the molecule. Therefore, the spectra of sulfur compounds show significant differences in the positions and/or the relative intensities of the absorption lines [215, 220, 221]. In principle, solid, liquid and gaseous samples can be measured. 

The XANES spectra of Se, Ss, Sio, S12, S14 [222] and polymeric sulfur [223, 224] are all very similar as far as the peak positions are concerned but the relative intensities of the two peaks differ considerably. The spectra are characterized by an absorption line at 2471.7 eV (so-called white line) and a broad absorption in the region 2477-2480 eV [222] see Fig. 35 (energies calibrated to the white line of ZnS04 defined as 2481.4 eV). Since the spectra of the components of a mixture are additive, quantitative analyses are possible, even for mixtures of samples as similar as Ss and polymeric sulfur, for instance [224]. The interpretation of the spectra is, however, still somewhat controversial see [225]. 

The charts are arranged in order of increasing element content. Correlations given in one chart (e.g. those for Cl I2 and CH3) are not repeated in subsequent charts. The frequency limits within which the band of a particular grouping is usually found are indicated by the black strips and extensions of the range to include unusual examples are shown as thin lines, e g. relative intensities are given in a very approximate fashion (see below). Both the position and the intensity of some absorptions are dependent on state, solvent, etc., and the actual frequency quoted is that most commonly observed. 

Kamat et al. [1.85] described a process by which the water content in freeze dried sucrose is measured by infra-red spectroscopy (A = 1000 to 2500 nm) and a newly developed fiber optic (Fig. 1.98). However, whether an interpretation of the absorption lines with respect to the water content is possible must be investigated from product to product. The location of the lines and their relative intensity can prevent their necessary discrimination. For pure... 

The intensity of a Mossbauer spectrum depends not only on the recoil-free fractions of the source and the absorber and on the number of absorbing nuclei, but also on the linewidth of the absorption lines and on whether or not saturation effects occur. The following approximate expression is valid for relatively thin absorbers [17] ... 

Thus, we can predict the relative intensity of each 0 m absorption line using this expression together with Equation (5.30) ... 

Excitation wavelength dependence of the Raman lines presents another complication that is not a problem for transient absorption measurements. For example, in comparing spectra taken at two different excitation wavelengths, one must consider not only which and in what proportion each molecular species is pumped, but also keep in mind what differences in relative intensity of the Raman lines result from excitation at the two exciting wavelengths. The complication can usually be overcome, especially when the spectra of the two species are well resolved. 

Figure 3.3 shows some of these possible transitions for HCI. Those with A7 = +1 are known as the R branch and occur at the high-energy side of the hypothetical transition At = 1, A7 = 0 (this is not allowed because of the selection rule, A7 = +1). Those with A7 = — 1 on the low-frequency side of the hypothetical transition form the P branch. Figure 3.4 shows the absorption spectrum of HCI at room temperature, with the rotational transitions responsible for each line. The relative intensities of the lines reflect the relative populations of the absorbing rotational levels the peaks are doublets due to the separate absorptions of the two chlorine isotopes, that is, H35C1 and H37C1, which have different reduced masses and hence values of the rotational constant B. 

Figures 24 and 25 demonstrate the success of deconvolution beyond the Doppler limit. Trace (a) in both figures is the undeconvolved data and represents the result of signal averaging over a large number of scans to produce a signal-to-noise ratio of approximately 300 1. The spectra were base-line corrected using a 0% absorption corresponding to the apparent base line between lines and a 100% absorption level was assumed, which gave reasonable relative intensities for the range of J values observed. The...

The collision-induced background of the dimer bands seen in the lower part of Fig. 3.39 shows a broad dip of absorption (the difference between the dashed line and the measured trace). Nearly symmetrically with the H2 61 (0) transition frequency (at 4161.1 cm-1) a series of sharp and intense absorption lines is seen that are resolved in the next two figures. The nature of the dip will become apparent below when we consider line shape computations they are related to the impossibility of bound-to-free and free-to-bound transitions at small frequency shifts relative to the H2 rotovibrational transition frequencies and are quite general. We simply state that the dimer dip is a two-body spectral feature whereas the... 

Analysis of the microwave spectrum of piperidine and of A-deuteropiper-idine suggests that the strongest Q-branch series together with the associated R-branch lines arise from the N-H-axial conformer.144 From this absorption and from a weaker series of Q branches, /eq//aj (the relative intensities of the type-A lines of /V-Hcq and N-Hax conformers corrected for the frequency factor) was estimated as 1/6 at — 34°C. This ratio is related to AE = En Hax - jv-Hcq by the expression... 

A Mossbauer spectrum contains different absorption peaks. The relative intensity, position, and shape of the absorption peaks composing the spectrum are related to the hyperfine interactions affecting the sample nuclei. The 57Co nuclei contained in the source are included in a solid matrix, such as a face-centered cubic (FCC) rhodium, which only affects the position of the emission line but does not split it [140],... 

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