Radiation of a nonrelativistic particle during its finite motion in a central field
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Radiation of a Nonrelativistic Particle during Its Finite Motion in a Central Field B. M. Karnakov*, Ph. A. Korneev**, and S. V. Popruzhenko Moscow Institute of Engineering Physics (State University), Kashirskoe sh. 31, Moscow, 115409 Russia *e-mail: [email protected] **e-mail: [email protected] Received July 2, 2007
Abstract—The spectrum and expressions for the intensity of dipole radiation lines are obtained for a classical nonrelativistic charged particle that executes a finite aperiodic motion in an arbitrary central field along a nonclosed trajectory. It is shown that, in this case of a conditionally periodic motion, the radiaton spectrum consists of two series of equally spaced lines. It is pointed out that, according to the correspondence principle, the rise of two such series in the classical theory corresponds to the well-known selection rule |∆l | = 1 for the dipole radiation in a central field in quantum theory, where l is the orbital angular momentum of the particle. The results obtained can be applied to the description of the radiation and the absorption of a classical collisionless electron plasma in nanoparticles irradiated by an intense laser field. As an example, the rate of collisionless absorption of electromagnetic wave energy in equilibrium isotropic nanoplasma is calculated. PACS numbers: 52.25.Os, 52.38.Dx, 52.50.Jm DOI: 10.1134/S1063776108040031
1. INTRODUCTION In recent years, there has been considerable interest in the physics of nanostructures irradiated by intense laser fields. This is primarily associated with the development of new experimental facilities for designing nano-objects with prescribed and well-controlled properties, such as clusters, thin films, and nanotubes. The emergence of high-power femtosecond lasers has stimulated new experiments on the interaction of nanoparticles with intense electromagnetic radiation. The irradiation of nanosystems by short laser pulses of intensity above 1014 W/cm2 leads to the internal ionization of the nanosystem and gives rise to a plasma with the mean energy of electrons ranging from tens to tens of thousands of electronvolts.1 Part of electrons leave the system (external ionization), thus giving rise to noncompensated charge that forms a barrier for the remaining plasma, which evolves in a finite volume up to the decay of the ionic core of the nanobody. The characteristic expansion time of the electron subsystem varies from tens of femtoseconds to several picoseconds. Thus, a new physical object arises on a femtosecond time scale—a dense hot electron plasma localized within a nanometer space scale—a nanoplasma [1, 2]. The physical properties of nanoplasma are now intensively investigated both theoretically and experimentally [3–6]. 1 At
laser field intensities above 1018 W/cm2, electrons in plasma become relativistic.
The scenario of interaction between nanoplasma and intense laser pulses depends on many parameters (the duration and the intensity of a pulse, the radiation wavelength, and the structure and the si
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