  A unified scheme using the R-matrix method has been developed for
electron-ion recombination subsuming heretofore separate treatments of
radiative and dielectronic recombination (RR and DR). The ab initio coupled
channel approach unifies resonant and non-resonant phenomena, and enables a
general and self-consistent treatment of photoionization and electron-ion
recombination employing idential wavefunction expansion. Detailed balance takes
account of interference effects due to resonances in cross sections, calculated
explicitly for a large number of recombined (e+ion) bound levels over extended
energy regions. The theory of DR by Bell and Seaton is adapted for high-n
resonances in the region below series limits. The R-matrix method is employed
for (A) partial and total photoionization and photorecombination cross sections
of (e+ion) bound levels, and (B) DR and (e+ion) scattering cross sections.
Relativistic effects and fine structure are considered in the Breit-Pauli
approximation. Effects such as radiation damping may be taken into account
where necessary. Unfiied recombination cross sections are in excellent
agreement with measurements on ion storage rings to about 10-20%. In addition
to high accuracy, the strengths of the method are: (I) both total and
level-specific cross sections and rate coefficients are obtained, and (II) a
single (e+ion) recombination rate coefficient for any given atom or ion is
obtained over the entire temperature range of practical importance in
laboratory and astrophysical plasmas, (III) self-consistent results are
obtained for photoionization and recombination; comprehensive datasets have
been computed for over 50 atoms and ions. Selected data are presented for iron
ions.
