Photoionization mode

About: Photoionization mode is a research topic. Over the lifetime, 1365 publications have been published within this topic receiving 26283 citations.

Creation of an Ultracold Neutral Plasma

Abstract: The study of ionized gases in neutral plasma physics spans temperatures ranging from 10 16 K in the magnetosphere of a pulsar to 300 K in the earth’s ionosphere [1]. At lower temperatures, the properties of plasmas are expected to differ significantly. For instance, three-body recombination, which is prevalent in high temperature plasmas, should be suppressed [2]. If the thermal energy of the particles is less than the Coulomb interaction energy, the plasma becomes strongly coupled, and the usual hydrodynamic equations of motion and collective mode dispersion relations are no longer valid [3]. Strongly coupled plasmas are difficult to produce in the laboratory and only a handful of examples exist [4], but such plasmas do occur naturally in astrophysical systems. In this work, we create an ultracold neutral plasma with an electron temperature as low as Te 100 mK, an ion temperature as low as Ti 10 mK, and densities as high as n 2 3 10 9 cm 23 . We obtain this novel plasma by photoionization of laser-cooled xenon atoms. Within the experimentally accessible ranges of temperatures and densities, both components can be simultaneously strongly coupled. A simple model describes the evolution of the plasma in terms of the competition between the kinetic energy of the electrons and the Coulomb attraction between electrons and ions. A numerical calculation accurately reproduces the data. Photoionization and laser cooling have been used before in plasma experiments. Photoionization in a 600 K Cs vapor cell produced a plasma with Te $ 2000 K [5], and a strongly coupled non-neutral plasma was created by laser cooling magnetically trapped Be 1 ions [6]. A plasma is often defined as an ionized gas in which the charged particles exhibit collective effects [7]. The length scale which divides individual particle behavior and collective behavior is the Debye screening length lD. It is the distance over which an electric field is screened by redistribution of electrons in the plasma, and is given by lD p

VUV and Soft X-Ray Photoionization

Abstract: Theory of Photoionization: VUV and Soft Xray Region M.Ya. Amusia. Manyelectron Effects in Photoionization M. Kutzner. Fundamental Aspects of Atomic Photoionization with High Brightness Light Sources A.F. Starace, S.T. Manson. Core Relaxation Effects in Molecular Photoionization J. Schirmer, et al. Partial Cross Sections and Angular Distributions U. Becker, D.A. Shirley. High Resolution Electron Spectrometry of Atoms M.O. Krause, C.D. Caldwell. Valence Ionization Processes in the VUV Region J. Berkowitz, et al. Photoionpair Formation J. Berkowitz. Electronic and Nuclear Relaxation of Core Excited Molecules I. Nenner, P. Morin. Resonances and Nearthreshold Processes G.C. King, K.H. Schartner. Resonant and Nonresonant Auger Recombination H. Aksela, et al. Laserbased UV and VUV Spectroscopy of Doubly-excited Atoms J.P. Connerade. Ion Yield Spectroscopy with Soft Xrays T. Hayaishi, P. Zimmermann. Coincidence Measurements on Ions and Electrons J.H.D. Eland, V. Schmidt. Spin Polarization in Photoionization U. Heinzmann, N.A. Cherepkov. Photoionization of Excited and Ionized Systems F.J. Wuilleumier, J.B. West. Photoionization of Oriented Systems and Circular Dichroism G. Schonhense, J. Hormes. Index.

Absolute Cross Sections for Molecular Photoabsorption, Partial Photoionization, and Ionic Photofragmentation Processes

Abstract: A compilation is provided of absolute total photoabsorption and partial‐channel photoionization cross sections for the valence shells of selected molecules, including diatomics (H2, N2, O2, CO, NO) and triatomics (CO2, N2O), simple hydrides (H2O, NH3, CH4), hydrogen halides (HF, HCl, HBr, HI), sulfur compounds (H2S, CS2, OCS, SO2, SF6), and chlorine compounds (Cl2, CCl4). The partial‐channel cross sections presented refer to production of the individual electronic states of molecular ions and also to production of parent and specific fragment ions, as functions of incident photon energy, typically from ∼20 to 100 eV. Total photoabsorption cross sections above the first ionization threshold are reported from conventional optical measurements obtained using line and continuum sources and from ‘‘equivalent‐photon’’ dipole (e,e) electron scattering experiments. Partial photoionization cross sections for production of electronic states of molecular ions are obtained from photoelectron spectroscopy and from dip...