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Vibronic coupling of electronic states. III. The definitive breakdown of the CBO potential picture within the framework of our model

The definitive breakdown of the CBO potential picture in consequence of the vibronic coupling of two electronic states is discussed on the basis of our model. The present treatment differs from that given in the literature.     

Point-form quantum field theory and meson form factors

We comment on canonical quantization of relativistic field theories on a Lorentz-invariant surface of the form x ² = τ². By this choice of the quantization surface all components of the four-momentum operator become interaction dependent, whereas the generators of Lorentz transformations stay free of interactions – a feature characteristic for Dirac’s “point-form” of relativistic dynamics. In the sequel we demonstrate how field theoretical concepts may enter the framework of relativistic quantum mechanics. To this aim we employ a Poincaré-invariant approximation scheme, which allows to reduce a field theoretical many-body problem to a multichannel problem for a Bakamjian-Thomas-type mass operator. As an application of this multichannel formalism we will discuss the scattering of an electron by a (confined) quark-antiquark pair. It will be sketched how an electromagnetic meson form factor can be extracted from the one-photon exchange optical potential.     

Simultaneous reconstruction of absorption and scattering images by multichannel measurement of purely temporal data

We present what is believed to be the first simultaneous reconstruction of the internal scattering and absorbing properties of a highly scattering medium by use of purely temporal data. These results are also the first acquired with the multichannel time-resolved imaging system developed at University College London.     

Sensitivity optimization in amplitude-modulated CW-EPR experiment

A sensitivity of recently developed method of amplitude-modulated continuous wave EPR (AM-CW-EPR) is studied depending on the parameters of the modulation field. The case of the significant saturation and high modulation frequency is addressed. It is found, that the rapid resonance passage effect is essential for AM-CW-EPR. However, its manifestation is different comparing to the conventional CW-EPR experiment. Both experimental data and numerical simulations support the enhancement of the AM-CW-EPR sensitivity under the rapid passage conditions for the modulating magnetic field, which is important for practical use of the method.     

Chemie des 5,7-Dihydroxy-2H-thiopyrano[2,3-b]pyridin-4(3H)-ons

Hydrolysis of the 4-alkyliminothiopyrano[2,3-b]pyridinedioles (5) and 4-alkylaminothiopyrano[2,3-b]pyridones (6) resp. with 10% NaOH gives 5,7-dihydroxy-2H-thiopyrano[2,3-b]pyridine-4(3H)-one (7).7 can be obtained in better yield by reaction of 4-dimethylamino-2(1H)-pyridinethione (8) with bistrichlorphenylethylamlonate (2). Aminolysis of7 affords the two isomeric products5 and6. On treatment with hydrazines,7 reacts only to 4-hydrazonoderivatives5. By heating in bromobenzene5d is cyclisized to 1H-5,1,2,6-thiatriaza-acenaphthylen-7-ol (11). On methylation with methyljodide5,6 and7 furnish the 7-methoxyproducts13,14 and12. By heating in 20% NaOH7 is transformed into the 2-thioxo-3-pyridylmethylketone16 A and its tautomer, 2-mercapto-3-pyridylmethylketone16 B. The structures of5,6 and7 are discussed.