关键词: 等离子体/
光致电离/
原子过程/
光谱
English Abstract
Excitation processes in experimental photoionized plasmas
Han Bo1,2,Wang Fei-Lu1,2,
Liang Gui-Yun1,
Zhao Gang1,2
1.Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China;
2.University of Chinese Academy of Sciences, Beijing 100049, China
Fund Project:Project supported by the National Basic Research Program of China (Grant No. 2013CBA01503), and the National Natural Science Foundation of China (Grant Nos. 11573040, 11135012, 11273032).Received Date:21 January 2016
Accepted Date:02 March 2016
Published Online:05 June 2016
Abstract:Photoionized plasmas widely exist nearby strong radiative sources in the universe. With the development of the high energy density facilities, photoionized plasmas related to astrophysical objects are generated in laboratories accordingly. RCF (radiative collisional code based on the flexible atomic code) is a theoretical model applied to steady-state photoionized plasmas. Its rate equation includes five groups of mutually inverse atomic processes, which are spontaneous decay and photoexcitation, electron impact excitation and deexcitation, photoionization and radiative recombination, electron impact ionization and three body recombination, autoionization and dielectronic capture. All of the atomic data are calculated by FAC (the flexible atomic code), and with four input parameters, RCF can calculate the charge distribution and emission spectrum of the plasma. RCF has well simulated the charge state distribution of a photoionizing Fe experiment on Z-facility and the measured spectrum of photoionizing Si experiment on GEKKO-XII laser facility. According to the simulation results, the importance of photoexcitation and electron impact excitation processes in the two photoionization experiments is discussed. In the photoionizing Fe experiment condition, high energy photons not only ionize the ions by photoionization directly, but also excite the ions to autoionizing levels, ionizing the ions indirectly. What is more, far from ionizing the ions, electrons even suppress the ionization of the plasma by exciting the ions to levels with small ionization cross sections. In the photoionizing Si experiment condition, because of high photoexcitation rate, strong resonance line of He-like ion and some Li-like ion lines, which have similar spontaneous decay rates as the resonance line, are emitted. Although the intercombination line of He-like ion has lower spontaneous decay rate than the resonance lines, strong recombination makes them have comparable strengthes. Electron impact excitation can influence the line ratio of He-like ion lines by affecting the distribution of 1s2l (l=s,p) levels.
Keywords: plasma/
photoionization/
atomic processes/
spectrum
