ANALYTICAL CROSS-SECTIONS AND RATE COEFFICIENTS FOR H-H INELASTIC-COLLISIONS

Analytical expressions for cross sections and the corresponding Maxwellian rate coefficients for direct excitation and ionization in binary collisions of hydrogen atoms axe evaluated by using the classical impulse approximation. The maximum values of the ionization and excitation cross sections and the positions of the maxima are also predicted. The classical impulse approximation cross sections were compared with available measurements and quantum-mechanical cross sections. The classical impulse approximation rate coefficients calculated were compared to the commonly used semi-empirical rate coefficients of Drawin. The comparison indicates that the commonly used semi-empirical rate coefficients are significantly higher than the classical impulse approximation rates for excitation and ionization transitions from excited levels.