Determination of state-to-state electron-impact rate coefficients between Ar excited states: a review of combined diagnostic experiments in afterglow plasmas

Electron-impact excitation processes play an important role in low-temperature plasma physics. Cross section and rate coefficient data for electron-impact processes from the ground state to excited states or between two excited states are required for both diagnostics and modeling works. However, the collisional processes between excited states are much less investigated than the ones involving the ground state due to various experimental challenges. Recently, a method for determining electron excitation rate coefficients between Ar excited states in afterglow plasmas was successfully implemented and further developed to obtain large sets of collisional data. This method combines diagnostics for electron temperature, electron density, and excited species densities and kinetic modeling of excited species, from which the electron excitation rate coefficients from one of the 1s states to the other 1s states or to one of 2p or 3p states are determined (states are in Paschen's notation). This paper reviews the above method—namely the combined diagnostics and modeling in afterglow plasmas. The results from other important approaches, including electron-beam measurement of cross sections, laser pump-probe technique for measuring rate coefficients, and theoretical calculations by R-matrix and distorted-wave models are also discussed. From a comparative study of these results, a fitted mathematical expression of excitation rate coefficients is obtained for the electron temperature range of 1–5 eV, which can be used for the collisional-radiative modeling of low-temperature Ar plasmas. At last, we report the limitations in the present dataset and give some suggestions for future work in this area.

[1]  R. McEachran,et al.  An optical potential method for elastic electron and positron scattering from argon , 2009 .

[2]  Xi-Ming Zhu,et al.  A simple collisional–radiative model for low-temperature argon discharges with pressure ranging from 1 Pa to atmospheric pressure: kinetics of Paschen 1s and 2p levels , 2010 .

[3]  U. Czarnetzki,et al.  2D collisional-radiative model for non-uniform argon plasmas: with or without ‘escape factor’ , 2015 .

[4]  U. Czarnetzki,et al.  Quenching rate constants for reactions of Ar(4p′[1/2]0, 4p[1/2]0, 4p[3/2]2, and 4p[5/2]2) atoms with 22 reagent gases , 2001 .

[5]  J. Boffard,et al.  Electron-impact excitation cross sections of the higher argon 3 p 5 np ( n = 5 , 6 , 7 ) levels , 2003 .

[6]  A. Wendt,et al.  Measurement of metastable and resonance level densities in rare-gas plasmas by optical emission spectroscopy , 2009 .

[7]  R. Srivastava,et al.  Excitation of the metastable states of the noble gases (10 pages) , 2006 .

[8]  Yi-Kang Pu,et al.  Optical emission spectroscopy in low-temperature plasmas containing argon and nitrogen: determination of the electron temperature and density by the line-ratio method , 2010 .

[9]  Vincent Puech,et al.  Comparisons of sets of electron–neutral scattering cross sections and swarm parameters in noble gases: III. Krypton and xenon , 2013 .

[10]  G. Piech,et al.  Measurement of electron-impact excitation cross sections out of metastable levels of argon and comparison with ground-state excitation , 1999 .

[11]  K. Bartschat,et al.  Close-coupling calculations for electron–atom collisions: benchmark studies and uncertainty estimates , 2015 .

[12]  F. Fehsenfeld,et al.  Afterglow Studies of the Reactions He+, He(23S), and O+ with Vibrationally Excited N2 , 1968 .

[13]  J. E. Chilton,et al.  Measurement of electron-impact excitation into the 3 p 5 4 p levels of argon using Fourier-transform spectroscopy , 1998 .

[14]  K. Bartschat,et al.  Electron impact excitation of the lowest doublet and quartet core-excited autoionizing states in Rb atoms , 2013 .

[15]  N. Sadeghi,et al.  Rate coefficients for collisional population transfer between 3p/sup 5/4p argon levels at 300 /sup 0/K , 1978 .

[16]  A. V. Phelps,et al.  Comparisons of sets of electron–neutral scattering cross sections and swarm parameters in noble gases: I. Argon , 2013 .

[17]  R. Boswell,et al.  Measurement of the electron density in atmospheric-pressure low-temperature argon discharges by line-ratio method of optical emission spectroscopy , 2009 .

[18]  U. Czarnetzki,et al.  Self-absorption method in combination with an optical probe: a possibility to determine the radial density profile of rare-gas metastables in low-temperature plasmas , 2015 .

[19]  Fei Liu,et al.  Determination of the rate coefficients of the electron-impact excitation from the metastable states to 2p states of argon by the emission line ratios in an afterglow plasma , 2014 .

[20]  Leendert Vriens,et al.  Cross-section and rate formulas for electron-impact ionization, excitation, deexcitation, and total depopulation of excited atoms , 1980 .

[21]  S. Trajmar,et al.  Benchmark measurements of cross sections for electron collisions: Analysis of scattered electrons , 1994 .

[22]  K. Bartschat,et al.  The B-spline R-matrix method for atomic processes: application to atomic structure, electron collisions and photoionization , 2013 .

[23]  E. Barnat.  Multi-dimensional optical and laser-based diagnostics of low-temperature ionized plasma discharges , 2011 .

[24]  E. Gargioni,et al.  Electron scattering from argon: Data evaluation and consistency , 2008 .

[25]  N. Sadeghi,et al.  Electronic energy transfer between state selected metastable argon atoms and ground state krypton atoms , 1983 .

[26]  Kock,et al.  Unified set of atomic transition probabilities for neutral argon. , 1989, Physical review. A, General physics.

[27]  Fei Liu,et al.  Determination of the rate coefficient of the electron-impact excitation from the argon resonance states (1s2 and 1s4) to 2p states by the emission line ratio in an afterglow plasma , 2015 .

[28]  W. W. Robertson,et al.  Spectra Excited in an Argon Afterglow , 1964 .

[29]  N. Sadeghi,et al.  Determination of electron-impact transfer rate coefficients between argon 1s2 and 1s3 states by laser pump–probe technique , 2013 .

[30]  Fei Liu,et al.  Determination of the electron-impact transfer rate coefficients between the Ar(1s) states in an afterglow discharge , 2014 .

[31]  O. Bochkova,et al.  Population of resonant levels in argon by ine lastic collision between slow electrons and metastable atoms , 1975 .

[32]  Gmw Gerrit Kroesen,et al.  Electron impact transfer rates between metastable and resonant states of argon investigated by laser pump–probe technique , 2015 .

[33]  L. Anderson,et al.  Principles and methods for measurement of electron impact excitation cross sections for atoms and molecules by optical techniques , 1994 .

[34]  L. Anderson,et al.  Excitation into3p55plevels from the metastable levels of Ar , 2007 .

[35]  Fei Liu,et al.  Measurement of the electron-impact excitation rate coefficients from argon 1s states to 3p states , 2015 .

[36]  G. García,et al.  Screening corrections for calculation of electron scattering from polyatomic molecules , 2003 .

[37]  G. Kroesen,et al.  Experimental evidence of resonant energy collisional transfers between argon 1s and 2p states and ground state H atoms by laser collisional induced fluorescence , 2015 .

[38]  L. Anderson,et al.  Electron-Impact Excitation of Rare-Gas Atoms from the Ground Level and Metastable Levels , 2007 .

[39]  V. Zeman,et al.  Electron-impact excitation from the(3p54s)metastable states of argon , 1999 .

[40]  J. Vlček,et al.  A collisional-radiative model applicable to argon discharges over a wide range of conditions. I. Formulation and basic data , 1989 .

[41]  J. Kurepa,et al.  Integral cross sections for electron-impact excitation of the 33S and 31S states of He near threshold , 2006 .

[42]  T. Sakurai,et al.  Decay of Metastable Argon Atoms in the Afterglow Plasma , 1998 .

[43]  A. V. Phelps,et al.  MOMENTUM TRANSFER CROSS SECTIONS FOR SLOW ELECTRONS IN HE, AR, KR, AND XE FROM TRANSPORT COEFFICIENTS, , 1964 .

[44]  Klaus Bartschat,et al.  Computational methods for electron–atom collisions in plasma applications , 2013 .

[45]  K. Bartschat,et al.  Electron-impact excitation of argon at intermediate energies , 2014 .

[46]  V. M. Donnelly.  Plasma electron temperatures and electron energy distributions measured by trace rare gases optical emission spectroscopy , 2004 .

[47]  P. Teubner,et al.  Electron-impact excitation of the (5d106s)2S1/2-(5d106p)2P1/2,3/2 resonance transitions in gold atoms , 2008 .

[48]  D. Uhrlandt,et al.  Transport mechanisms of metastable and resonance atoms in a gas discharge plasma , 2013 .