The total cross-sections for reactions between alkali metal atoms and halogen molecules are given in the table below (R.D. Levine and R.B. Bernstein, Molecular reaction dynamics, Clarendon Press, Oxford, 72 (1974)). Assess the data in terms of the harpoon mechanism.

Electron affinities are approximately 1.3 eV (CI2), 1.2 eV (Br2), and 1.7 eV (I2), and ionization energies are 5.1 eV (Na), 4.3 eV (K), 4.2 eV (Rb), and 3.9 eV (Cs).

o*/nm? Cl, Brz Na 1.24 1.16 0.97 K 1.54 1.51 1.27 Rb 1.90 1.97 1.67 Cs 1.96 2.04 1.95