A Laricchiuta IMIPCNR sezione di Bari Italy MODELING

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

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 N 2 VIBRONIC EXCITATION and (PRE)DISSOCIATION of O 2 and N 2 RESONANT VIBRATIONAL EXCITATION of N 2

IONIZATION N 2 -N 2+ 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 ionization potential SIMPLIFIED APPROACH

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 cm 2]

CROSS SECTION DEPENDENCE on the INITIAL VIBRATIONAL QUANTUM NUMBER

ELECTRON-IMPACT IONIZATION from GROUND STATE cross section [10 -17 cm 2] ionic state Van Zyl 0. 320 0. 535 0. 145 this work 0. 30 0. 50 0. 20 E=100 e. V [J. Geophys. Res. 100, 23755 (1995)]

ELECTRON-IMPACT IONIZATION from EXCITED STATE

EXCITATION-DISSOCIATION VIBRONIC EXCITATION PREDISSOCIATION DIRECT DISSOCIATION

A* e A* DIRECT DISSOCIATION VIBRONIC EXCITATION n’ PREDISSOCIATION curves crossing X M 2 M+M M 2* M+M

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

Electron Impact Excitation/Dissociation Theoretical Approach: IMPACT PARAMETER METHOD ü SEMICLASSICAl Method (quantal target - classical electron projectile) ü ALLOWED Transitions ü Degenerate Rotational Levels A. U. Hazi, Phys. Rev. A 5, 23 (1981) M. J. Redmon, B. C. Garrett, L. T. Redmon, C. W. Mc. Curdy, 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 ) G Potential Energy Curves Transition Dipole Moment O S Pa Im ra pa m ct et er FAUST BORN Cross Section IMPACT Cross Section

O 2 system POTENTIAL ENERGY CURVES: Schumann-Runge transition

DISSOCIATIVE O 2 CHANNELS E=30 e. V

CROSS SECTION DEPENDENCE on the INITIAL VIBRATIONAL QUANTUM NUMBER E=30 e. V

O 2 THEORETICAL GLOBAL DISSOCIATIVE RATE COEFFICIENTS

STATE-TO-STATE CROSS SECTIONS E=30 e. V nf = 4 nf = 7 nf = 11

COMPARISON with EXPERIMENTS ni = 0

N 2 W. C. Ermler, J. Phys. Chem. 86, 1305 (1982)

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

theoretical global predissociative rate coefficients

The N 2 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 1 Sg (ni) b 1 Pu E=40 e. V X 1 Sg (ni) b 1 Pu (continuum) E=40 e. V

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 N 2 (n, j=0) O 2 (n, j=0)

RESONANT VIBRATIONAL EXCITATION resonant electron capture electron detachment

resonant vibrational excitation cross section (Schwinger multichannel method) N 2 resonant vibrational excitation rate coefficients J=50 W. M. Huo, V. Mc. Koy, 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 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