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Valency angle light

This valency angle is no new idea in organic chemistry. The essential fact is that this angle is now obtained directly for the first time by means of vector combination of the moments. Hitherto, however, it has only been possible to carry out these calculations for a few substances. Hence the fact is of importance that (as I shall show by means of one or two examples) the depolarization of scattered light and the Kerr effect enable us to prove the existence of such angles and to calculate their value, even when free rotation, which gives rise to errors in the vectorial combination, is present. [Pg.120]

Equation (A4-21) allows the theoretically important end-to-end chain distance to be calculated from the experimentally accessible (e.g., by light scattering measurements) radius of gyration. This calculation remains valid for the linear valence angle chain and the linear valence angle chain with hindered rotation, but is not valid for polymers in good solvents. [Pg.147]

Fig. 7.3. The hydrogen bond valence, >Sh, as a function of 0-0 distance. The heavy line shows the most probable distance, the light lines indicate the range of permitted values depending on the O-H. .. O angle. The straight broken line is calculated from eqn (7.1) and is a linear fit to the heavy line for iSh < 0.4 vu. Fig. 7.3. The hydrogen bond valence, >Sh, as a function of 0-0 distance. The heavy line shows the most probable distance, the light lines indicate the range of permitted values depending on the O-H. .. O angle. The straight broken line is calculated from eqn (7.1) and is a linear fit to the heavy line for iSh < 0.4 vu.
The measurements were carried out using polarized-light from synchrotron radiation. The angle-resolved UPS spectra were recorded for specific directions of photon incidence, photon polarization, and electron exit, chosen in order to resolve the momentum dependence of the 7t-electron energy bands which could be observed in this experiment. Details are available elsewhere63. The UPS results are analysed not only with the help of the valence effective Hamiltonian (VEH) method, but also with the help of new quantum-chemical calculations based upon the excitation model method64. The full VEH band structure is shown in Fig. 7.32. [Pg.127]

Fig. 5.7 Left spin resolved photoemission spectra for thin iron films on W(llO) taken with unpolarized light (hv = 21.22 eV). Right spin integrated spectra taken with circularly polarized radiation (hv = 21.2 eV) for emission angles between 0° < 6 < 15°. The thin lines in the MCDAD spectra mark the position of the valence band maxima in normal emission. Reprinted from [26], Copyright (1998), with permission from Elsevier... Fig. 5.7 Left spin resolved photoemission spectra for thin iron films on W(llO) taken with unpolarized light (hv = 21.22 eV). Right spin integrated spectra taken with circularly polarized radiation (hv = 21.2 eV) for emission angles between 0° < 6 < 15°. The thin lines in the MCDAD spectra mark the position of the valence band maxima in normal emission. Reprinted from [26], Copyright (1998), with permission from Elsevier...
In everyday practice, chemists often use a minimal model of molecules that enables them to compare the geometry and vibrational frequencies with experiment to the accuracy of about 0.01 A for bond lengths and about 1 for bond angles. This model assumes that the speed of light is infinite (non-relativistic effects only), the Born-Oppenheimer approximation is valid (i.e., the molecule has a 3-D structure), the nuclei are boimd by chemical bonds and vibrate in a harmonic way, the molecule moves (translation) and rotates as a whole in space. In many cases, we can successfully predict the 3-D structure of a molecule by using a very simple took the Valence Shell Electron Pair Repulsion (VSEPR) algorithm. [Pg.500]


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Valency angle

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