Vibrational-intensity distribution

Vibrational intensity distributions have not been measured in any of the room... 

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). 

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... 

Zare R N 1964 Calculation of intensity distribution in the vibrational structure of electronic transitions the B... 

The intensity distribution among rotational transitions in a vibration-rotation band is governed principally by the Boltzmann distribution of population among the initial states, giving... 

In 1925, before the development of the Schrodinger equation, Franck put forward qualitative arguments to explain the various types of intensity distributions found in vibronic transitions. His conclusions were based on an appreciation of the fact that an electronic transition in a molecule takes place much more rapidly than a vibrational transition so that, in a vibronic transition, the nuclei have very nearly the same position and velocity before and after the transition. 

Figure 7.21 illustrates a particular case where the maximum of the v = 4 wave function near to the classical turning point is vertically above that of the v" = 0 wave function. The maximum contribution to the vibrational overlap integral is indicated by the solid line, but appreciable contributions extend to values of r within the dashed lines. Clearly, overlap integrals for A close to four are also appreciable and give an intensity distribution in the v" = 0 progression like that in Figure 7.22(b). 

Figure 7.22 Typical vibrational progression intensity distributions...

The influence of molecular vibrations on the interference pattern was first studied by James in 1932 He discussed the intensity distribution (of X-ray scattering) by vibrating molecules, and determined the dependence of the intensity distribution on the vibrational amplitudes. 

Figure 55. Comparison of relative intensity distributions of P-branch rotational lines of (3,9) and (4,10) bands of N2+ (C22 , e, m)-> N2+(V25>", m ) + hv spontaneous radiative transitions. Points are experimental data and solid lines are distributions computed using statistical phase-space model to determine N2 (C221), v, m) vibrational-rotational distribution resulting from reaction He+ + N2(V 2g, v, m)— N2+(C22M,o,m)+He.419...

To evaluate the thermodynamic and radiation properties of a natural or perturbed state of the upper atmosphere or ionosphere, the thermal and transport properties of heated air are required. Such properties are also of particular interest in plasma physics, in gas laser systems, and in basic studies of airglow and the aurora. In the latter area the release of certain chemical species into the upper atmosphere results in luminous clouds that display the resonance electronic-vibrational-rotational spectrum of the released species. Such spectra are seen in rocket releases of chemicals for upper-atmosphere studies and on reentry into the atmosphere of artificial satellites. Of particular interest in this connection are the observed spectra of certain metallic oxides and air diatomic species. From band-intensity distribution of the spectra and knowledge of the /-values for electronic and vibrational transitions, the local conditions of the atmosphere can be determined.1... 

The ligand-model vibrational spectroscopy approach has contributed strongly to fairly reliable identifications on metal surfaces of C2 species of the types 1, 2 (ethene type II spectra) (17), 3 (ethene type I spectra), 4 (ethene type I spectra), 8, and 13 (ethyne type B spectra) as well as to possible identifications of types 5, 7, 15 (ethyne type A spectra), 16, and 20. Approximate band positions and associated intensity distributions in the spectra from normal and perdeutero species should be considered together (/ 7). The correspondence of the infrared spectrum from 4 with type I spectra is less satisfactory for the C2D4 ligand than in most other cases. However an extra structural variable in this case is the degree of nonplanarity of the cyclic C2M2 skeleton, which may differ between the model compound and the surface species. 

However, ground state atoms, 0(3P), cannot be ignored. That they can produce vibrationally excited 02 is proved by shock tube studies of the rate of thermal decomposition of ozone41. This work, at reaction temperatures up to 900 °K, included absorption spectrography of the decomposing gas. The excited 02 were found with an intensity distribution (for the levels observed) similar to that obtained in photolytic experiments. Production of 0(1H) in the thermal decom-... 

Azulene has weak absorption in the visible region (near 7000 A) and more intense band systems in the ultraviolet. The first ultraviolet system, which commences at about 3500 A, has been examined in substitutional solid solution in naphthalene (Sidman and McClure, 1956) and in the vapour state (Hunt and Ross, 1962), and can be observed in fluorescence from the vapour (Hunt and Ross, 1956). Theory predicts that the transition is 1Al<-lAl(C2K), i.e. allowed by the electronic selection rules with polarization parallel to the twofold symmetry axis (see, e.g., Ham, 1960 Mofifitt, 1954 Pariser, 1956b). The vibrational analysis shows that the transition is allowed but does not establish the axis of polarization. The intensity distribution among the vibrational bands indicates a small increase in CC bond distance without change in symmetry. 

The intensity distributions of well resolved vibronic spectra recorded in absorption and emission at low temperature are used to determine the geometric distortions of the electronically excited states of coordination compounds. In particular for complexes of lower symmetry, band analysis is necessary leading to results with which bond distance changes can be calculated. For spectra exhibiting no vibrational fine structure, a new technique is proposed which uses time resolved methods, considering deviations from the Poisson distribution of photons by recording time intervals between two successively emitted photons. 

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