Collision Processes of Hydrogen Molecules

The quantum state of H2 molecule is characterized by the set of quantum numbers (N1 3A%,v ), where N1,3A refers to the electronic molecular state (N is the state principal quantum number in the united limit, A is the projection of total electron angular momentum, 1,3 (singlet, triplet) is the spin multiplicity of the state, a = g, u is the state symmetry, 7r is its parity) and v is the vibrational quantum number of N1,3A state. For simplicity, the indices (1,3), 7, 7r and A will, generally, be omitted in the reaction description. We note that many (NA) states of H2 have dissociative character. 

We start with the basic processes involved in the vibrational population of a given (NA) state. These processes include  

As mentioned above, the processes (19.24)-(19.29) have not been studied for electronically excited states of H2. An estimate of the cross-sections for processes (19.24), (19.27)-(19.29) for N 2 can be made by the SSH model. The available and relatively simple theoretical methods (such as the Born, Born-Rudge and impact-parameter method) can be used to calculate also the cross-section for reactions (19.26), but the difficulties of determining the higher resonant states of prevent easy estimates of cross-sections for reactions (19.25) when N 2. 

Electron-impact electronic excitation, ionization and dissociation processes are among the most important collision processes that H2 molecules undergo in a low-temperature plasma. These include 

Allowed excitation transitions are those between /V/1-states with different g, -symmetries, and most intense among them are those preserving the total spin (singlet-singlet and triplet-triplet transitions). The intermediary state in reaction (19.31) is a bound electronic state, but the transition takes place to the vibrational continuum of this state. The intermediary state in reaction (19.32) is a dissociative state that lies completely in the vibrational continuum. The reaction (19.33) is similar to reaction (19.26), except that the decay of (H ) resonance (auto-detachment) takes place in the vibrational continuum. 

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