IMIP-CNR, sezione di Bari, Italy A.Laricchiuta IMIP-CNR, sezione di Bari, Italy

!!!non-equilibrium conditions!!! MODELING of PLASMA SYSTEMS for AEROSPACE APPLICATIONS (shuttle re-entry simulation) !!!non-equilibrium conditions!!! STATE-to-STATE KINETIC APPROACH ELEMENTARY PROCESSES database of state-resolved cross sections molecular dynamic calculations molecular beam experiments

ELECTRON IMPACT induced PROCESSES in HOMONUCLEAR DIATOMIC MOLECULES NON-DISSOCIATIVE IONIZATION of N2 VIBRONIC EXCITATION and (PRE)DISSOCIATION of O2 and N2 RESONANT VIBRATIONAL EXCITATION of N2

N2-N2+ system POTENTIAL ENERGY CURVES IONIZATION N2-N2+ system POTENTIAL ENERGY CURVES F.R. Gilmore, J.Q.R.S.T. 5, 369 (1965)

ELECTRON-IMPACT IONIZATION: THEORETICAL APPROACH IONIZATION CROSS SECTION of atoms by electron impact CLASSICAL METHODS (THOMSON) ƒ universal function IONIZATION CROSS SECTION of vibrationally excited molecules by electron impact Franck-Condon factor SIMPLIFIED APPROACH ionization potential

we find the universal function f(x) on the basis of the experimental data NITROGEN

ELECTRON-IMPACT IONIZATION from GROUND STATE cross section [10-17 cm2]

CROSS SECTION DEPENDENCE on the INITIAL VIBRATIONAL QUANTUM NUMBER

ELECTRON-IMPACT IONIZATION from GROUND STATE cross section [10-17 cm2] ionic state Van Zyl this work 0.320 0.30 0.535 0.50 0.145 0.20 E=100eV [J.Geophys.Res. 100, 23755 (1995)]

ELECTRON-IMPACT IONIZATION from EXCITED STATE

EXCITATION-DISSOCIATION VIBRONIC EXCITATION PREDISSOCIATION DIRECT DISSOCIATION

e n’ A* M + M A* M2* M + M X M2 DIRECT DISSOCIATION VIBRONIC EXCITATION n’ M + M PREDISSOCIATION curves crossing X M2

intermediate energy region??? Impact Parameter Method cross section vibrational-dependence reasonable ACCURACY (agreement with experimental data) low computational cost BUT no treatment of resonance effects suitable only for allowed transitions threshold region high energy region quantistic effects (resonances) suitable for approximations (Born and Born-Bethe Approximations) accurate quantum treatments (R-Matrix, Close-Coupling …)

Electron Impact Excitation/Dissociation Theoretical Approach: IMPACT PARAMETER METHOD SEMICLASSICAl Method (quantal target - classical electron projectile) ALLOWED Transitions Degenerate Rotational Levels A.U. Hazi, Phys.Rev. A 5, 23 (1981) M.J. Redmon, B.C. Garrett, L.T. Redmon, C.W. McCurdy, Phys.Rev.A 32, R. Celiberto, T.N. Rescigno, Phys.Rev. A 47, 1939 (1993)

CODE SCHEME GAMESS (General Atomic and Molecular Electronic Structure System ) GOS FAUST BORN Cross Section Potential Energy Curves Transition Dipole Moment Impact Parameter IMPACT Cross Section

O2 system POTENTIAL ENERGY CURVES: Schumann-Runge transition

DISSOCIATIVE O2 CHANNELS E=30eV

CROSS SECTION DEPENDENCE on the INITIAL VIBRATIONAL QUANTUM NUMBER E=30eV

O2 THEORETICAL GLOBAL DISSOCIATIVE RATE COEFFICIENTS

STATE-TO-STATE CROSS SECTIONS E=30eV nf = 4 nf = 7 nf = 11

COMPARISON with EXPERIMENTS ni = 0

N2 W.C. Ermler, J. Phys. Chem. 86, 1305 (1982)

predissociative cross sections theoretical global predissociative cross sections P.C. Cosby, J. Chem. Phys. 98, 9544 (1993) n=0

predissociative rate coefficients theoretical global predissociative rate coefficients

The N2 Birge-Hopfield system Direct Dissociation through the excited state Vibronic Excitation Dissociation through Predissociative Channels D.Spelsberg, W.Meyer, Journal of Chemical Physics 115 (2001) 6438

X 1Sg (ni)  b 1Pu (continuum) E=40eV

CROSS SECTION DEPENDENCE on the INITIAL VIBRATIONAL QUANTUM NUMBER

E.C. Zipf, M.R. Gorman, Journal of Chemical Physics 73 (1980) 813

STATE-TO-STATE CROSS SECTIONS

COMPARISON of electron-molecule and atom-molecule collision RATE COEFFICIENTS N2 (n,j=0) O2 (n,j=0)

RESONANT VIBRATIONAL EXCITATION resonant electron capture electron detachment

N2 resonant vibrational excitation cross section (Schwinger multichannel method) N2 resonant vibrational excitation rate coefficients J=50 W.M. Huo, V.McKoy, M.A.P.Lima T.L.Gibson , in "Thermophysical aspects of reentry flows", J.N.Moss and C.D. Scott eds., AIAA, New York (1986).

M.Capitelli R.Celiberto B.M.Smirnov, A.V.Kosarim Department of Chemistry, University of Bari, Italy IMIP-CNR, sezione di Bari, Italy R.Celiberto DICA, Politecnico di Bari, Italy B.M.Smirnov, A.V.Kosarim Institute for High Temperatures of RAS, Moscow, Russia