Nucleon polarizabilities in the perturbative chiral quark model

The nucleon polarizabilities alpha(E) and beta(M) are studied in the context of the perturbative chiral quark model. We demonstrate that meson cloud effects are sufficient to explain the electric polarizability of nucleon. Contributions of excite quark states to the paramagnetic polarizability are dominant and cancel the diamagnetic polarizability arising from the chiral field. The obtained results are compared to data and other theoretical predictions.Comment: 25 pages, 18 figures, 2 table

On the feasibility of a nuclear exciton laser

Nuclear excitons known from M\"ossbauer spectroscopy describe coherent excitations of a large number of nuclei -- analogous to Dicke states (or Dicke super-radiance) in quantum optics. In this paper, we study the possibility of constructing a laser based on these coherent excitations. In contrast to the free electron laser (in its usual design), such a device would be based on stimulated emission and thus might offer certain advantages, e.g., regarding energy-momentum accuracy. Unfortunately, inserting realistic parameters, the window of operability is probably not open (yet) to present-day technology -- but our design should be feasible in the UV regime, for example.Comment: 7 pages RevTeX, 4 figure

ON THE COMPENSATION OF A NONUNLFORM CHEMICAL (MONOPOLE) SHIFT OF THE MÖSSBAUER LINE

La proportionnalité entre la densité totale d'électrons S et la densité de spin au site du noyau permet de proposer une méthode pour compenser par un champ de radio-fréquence approprié la raison essentielle d'élargissement des raies Mössbauer : le déplacement isomérique non uniforme. La méthode proposée pour restreindre la largeur des raies Mössbauer peut être appliquée à la détermination précise de certains paramètres d'i. h. f. et à l'élaboration d'un laser γ (gaser). Elle est également importante pour l'extension de la spectroscopie Mössbauer à tous les problèmes nécessitant des raies plus étroites (probablement jusqu'à la largeur de raie minimale de RMN en phase solide, c.-à-d. 10-15 eV).The proportionality between the small variations of total S-electron density and spin density at the site of nucleus location permits proposing a method of compensating by a properly chosen radiofrequency field the most essential source of Mössbauer line broadening : the non-uniform chemical (monopole) shift. The proposed method for narrowing of the Mössbauer lines can be used for precise determination of certain HFS parameters and for starting the operation of a γ-laser (gaser). It is also important for the extension of Mössbauer spectroscopy to all problems, which need much narrower lines (probably, up to the minimum width of solid state NMR line, i. e. ca 10-15 eV)