Quadrupole association and dissociation of hydrogen in the early
  Universe
  Radiative association and photodissociation rates are calculated for
quadrupole transitions of H2. A complete set of bound and unbound states are
included in a self-consistent master equation to obtain steady-state
concentrations for a dilute system of hydrogen atoms and molecules.
Phenomenological rate constants computed from the steady-state concentrations
satisfy detailed balance for any combination of matter and radiation
temperature. Simple formulas are derived for expressing the steady-state
distributions in terms of equilibrium distributions. The rate constant for
radiative association is found to be generally small for all temperature
combinations. The photodissociation rate constant for quadrupole transitions is
found to dominate the rate constants for other H2 photodestruction mechanisms
for radiation temperatures less than or equal to 3000 K. Implications for the
formation and destruction of H2 in the early universe are discussed.
