Dissociation of Hydrogen Molecules by Vibrational Excitation and Three-Body Recombination Coefficient. II

The recombination of two hydrogen atoms in the presence of a third in a thermal collision is considered, the principle of detailed balance being used to obtain the three-body coefficient C₃ from the cross section σ₂ of the reverse, dissociation process. This cross section is calculated by a method developed previously which depends on correcting the Born approximation by means of the exact one-dimensional problem. We consider the case when the molecule is formed in a highly excited vibrational state of the electronic ground state and the excess energy of several kT goes into translational energy of the third atom. The three-body coefficient in this case is of order 3×{}10^-36 cm⁶ sec^-1, which is still much smaller than the empirical values. Some estimate is made of the validity of the correction method.The excitation and de-excitation of the first vibrational state of hydrogen by collisions with protons is investigated, and it is found that an excited molecule requires 10³ to 10⁴ thermal collisions to lose its excitation; this is roughly of the correct order of magnitude for such processes.