Angular anisotropy of characteristic x-radiation and auger electrons during the resonance coherent excitation of relativ
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Angular Anisotropy of Characteristic X-Radiation and Auger Electrons during the Resonance Coherent Excitation of Relativistic Ions under Planar Channeling Conditions V. V. Balashov*, A. A. Sokolik, and A. V. Stysin Skobeltsyn Institute of Nuclear Physics, Moscow State University, Moscow, 119992 Russia *e-mail: [email protected] Received January 9, 2008
Abstract—The results of new experiments on the resonance coherent excitation of relativistic highly charged ions under planar channeling conditions are analyzed by a method of the generalized master equation for the density matrix of ions. The results of calculations pertaining to the angular anisotropy of characteristic electromagnetic radiation, to the survival fraction of ions as a function of the trajectory of their motion in the channel, and to the excitation of autoionizing states of helium-like ions under the double resonance coherent excitation are in close agreement with measurement data. New experiments are proposed. PACS numbers: 61.85.+p, 32.60.+i, 32.80.Zb, 32.90.+a DOI: 10.1134/S1063776108070133
1. INTRODUCTION A fast ion propagating through a crystal target in the planar channeling regime is subjected to the action of a time-periodic electric field of the crystal. At a certain relation between the velocity of the ion and the orientation of the propagating ion beam with respect to the crystal axes at which the frequency of the coherent action of lattice atoms on the ion proves to be equal to a particular eigenfrequency of its electron shell, the ion rapidly transits to an excited state. In this state, the ion either quickly loses its electron in a collision with an electron or atom of the target, or transits to a lowerlying state, emitting a characteristic photon. The phenomenon of the resonance coherent excitation (RCE) of channeled ions in crystals has been theoretically predicted by Okorokov in 1965; also, he was the first who theoretically and experimentally studied this effect [1]. The occurrence of the Okorokov effect has been proven in crucial experiments by Datz and collaborators [2], which were performed for the first time with highly charged ions. Their results have aroused considerable interest in the RCE process and have stimulated investigation of the theory of the effect [3–8]. At present, the most complete view of various aspects of the RCE process can be found in experiments performed by a joint group of researchers from universities and research centers of Tokyo who have systematically studied the RCE process since the 1980s [9]. Recently, this group has performed a series of studies involving a new approach to the very statement of the RCE experiment, which considerably extended the area of possible fundamental and applied investigations in this field. This series includes (i) an observation of the
Okorokov effect for nonchanneled ions [10], (ii) investigation of the trajectory-dependent RCE of channeled ions [11], (iii) an observation of the Okorokov effect upon simultaneous excitation of two transitio
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