Intensity anomalies

If the experimental lineshapes do not exhibit sub-bands and are asymmetric, or if they involve sub-bands, but with intensity anomalies with respect to the Franck-Condon progression law, then, together with the dephasing mechanism, damping of the slow mode ought to be also considered as occurring in a sensitive competitive way. 

A VEEL spectrum of the species formed by the decomposition of tert-butyl (2-methyl-2-propyl) chloride and bromide on Cu(100) at 185 and 120 K, respectively (193), shows intensity anomalies similar to those discussed for 2-propyl groups when interpreted in terms of surface terf-butyl groups. Further RAIRS and VEELS work is required. 

The HCP case exhibits one additional signal of the onset of rapid change in vibrational resonance structure. This is the sudden onset of vibrational perturbations at (0, 32, 0) [5]. Local perturbations, where one rotational term curve crosses another, are manifest as level shifts, extra lines, and intensity anomalies [18]. Such perturbations are typically rare at low vib and... 

While the intensity anomaly alone(item 1 above) can be due to our poor understanding of atmospheric structure and/or of line formation in the upper atmosphere, peculiar line shift and line asymmetry(item 2) as well as differential time variation note above(item 3) suggest that at least a part of low excitation lines should be originating not in the photosphere but in an extra layer well separated from the photosphere. We tentatively refer this separate extra layer as CO absorption layer (the "layer" does not necessarily imply that it is well stratified but rather it can also be an inhomogeneous component in outer atmosphere, and the "layer" is used in this extended meaning in what follows). 

In Check it 5.2.6.9 the effectiveness of the improved DEPT++ experiment is shown by comparing the results from a IH coupled DEPT experiment with those obtained using the DEPT sequence. The IH coupled experiments in the most effective way of illustrating this improvement because in the broadband IH decoupled each CH group is a singlet and phase and intensity anomalies are reduced to minor intensity changes. 

The existence of an anomaly in the spectrum of Ba+ had been known for many years. It was commented on by Saunders et al. [213], who remarked the perturbation. .. appears to be of a novel type but could advance no explanation for it. The realisation that this is due to a near-critical potential barrier effect came much later [212]. Hartree-Fock calculations were used to establish that the n/ wavefunctions of Ba+ become resonantly localised in the inner well of a double-well potential around n = 5. As a consequence, all the low n orbitals become distinctly bimodal or hybrid in character (as can be seen in fig. 5.12) with peaks in both the inner and the outer potential wells. This results in (i) an unusual course in the quantum defects for the nf series they are not constant, but depend strongly on the energy, despite the absence of any local perturbation (ii) a pronounced intensity anomaly in the 5d — nf excitation series, which was first noted by Roig and Tondello [214] and (iii) an anomaly in the course of the spin-orbit splittings for the first members of the series, both of which can be explained on the basis of the bimodal character of the... 

These conclusions of Houston and Hsieh were based on a complicated method of analysis of interferometer patterns which relied on the assumption that the line intensities were approximately as given by the theory. While this was very reasonable, the approach is too indirect to be entirely convincing. The conclusions were, however, reinforced by the direct measurements of Williams and Gibbs [141] and by further analysis of his plates by Houston [63], Other workers found no discrepancy with the theory apart from small intensity anomalies [38], [62], [123], [128]. 

Intensity anomalies were found by nearly all observers. Component (2) nearly always appeared stronger than (1), contrary to the theory. These anomalies were ascribed to the conditions prevailing inside the discharge tube, and were not looked upon as providing a test of the theory. 

Perturbations between States of the Same Symmetry Vibrational-Band Intensity Anomalies.380... 

There are also several perturbation-sensitive non-isolated molecule properties, such as collision-induced population anomalies (Radford and Broida, 1963) (Section 6.5.5) and differential pressure and power (Gottscho and Field, 1978) broadening efforts (Section 6.5.1). Since all of the isolated molecule properties are explicitly related to p, the following discussion focuses on p. Note, however, that the nature of a perturbation related intensity anomaly is profoundly dependent on whether /x 2, r, or (A, B, /, a) is being measured and on the state selectivity and spectral resolution of the specific experiment. 

A special class of intensity anomaly arises from E+ E perturbations. Ren-horn (1980) has shown that interference between two transition moments could account for the anomalous (2E — 2n3y2) / (2 — 2Ifi/2) subband intensity ratios observed by Appleblad, et al, (1981) in a CuO 2E — X2II transition at 767 nm. An unperturbed 2E —> 2II transition should have approximately equal intensity E — n3/2 and E — II1/2 subbands. The fi // interference effects discussed in Section 6.3.2 only affect R/P intensity ratios within a subband without changing the total subband intensity. 

The subband intensity anomaly arises from AS = 0, A Cl = 0, ff / 0, E+ E-spin-orbit perturbations combined with the opposite behavior of the phase factors for E+ — IIfi=1 versus E — IIn=i s transitions (Section 6.3.2). The nominal E+ and E eigenstates are... 

If the photon energy, hv, coincides with a superexcited state, AB, autoionization contributes extra intensity to the direct ionization signal. As a result, vibrational intensity distributions will not be described by Franck-Condon factors (see, for example, Caprace et at, 1976). These vibrational intensity anomalies may be explained similarly to the effect of perturbations on intensity borrowing (Section 6.2). 

Shape resonances are also responsible for intensity anomalies in the PES and ZEKE spectra of O2 (for example, Braunstein, et al, 1992). 

Cooper minima axe also responsible for non Franck-Condon vibrational intensity distributions and intensity anomalies observed in both PES and ZEKE spectra. As for atoms, when the photoionization transition corresponds to excitation from a Rydberg orbital having at least one radial node in its wavefunction, the... 

As noted in Section 8.1.2, numerous intensity anomalies are observed in ZEKE spectra. Most of them are due to autoionization. For the effects of rotational, vibrational, and electronic autoionizations, we refer to the work of Merkt and... 

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