### TOTAL ELECTRON-ION RECOMBINATION RATE COEFFICIENTS

###
A new unified method has been developed that treats both the
radiative and the di-electronic recombination (RR and DR) processes
in an * ab initio * manner, and yields total recombination rates
valid at all temperatures of practical interest in astrophysics and
laboratory applications.

While current methods treat the RR and DR separately, these two
processes are in principle unified in nature, as seen by the
extensive autoionization resonance structures in the OP photoionization
cross sections. Furthermore, previous mehtods are based on different
atomic physics approximations, valid in different temperature regimes
(e.g. low-T DR, high-T DR), leading to inconsistencies with (a) the OP
photoionization data, and (b) due to uncertainities in the different
treatments and ranges.

The method is described in Nahar and Pradhan (Phys.Rev.Letts 68,
1488,1992; Phys.Rev.A 49, 1816,1994; Ap.J. 447,966,1995). The
recombination calculations are carried out using the R-matrix method,
as in the OP work, for both the photoionization and the e-ion scattering
problem, in the close-coupling approximation, and using a new theory of
DR due to Bell and Seaton (1986). (The
OP data from Topbase may not in general be employed for recombination
calculations, since the latter require partial photoionization cross
sections into specific states of the parent ion.) The new recombination
rates are fully consistent with the photoionization data since both
are calculated using the same method, but more importantly, *the same
atomic eigenfunction expansion*.

TABLE OF RECOMBINATION RATE COEFFICIENTS
for electron-ion recombination rate coefficients for Si I, Si II, S II,
S III, C II, and C-like ions C I, N II, O III, F IV, Ne V, Na VI, Mg VI,
Al VIII, Si IX, and S XI,
(Sultana N. Nahar, ApJS 101, 423, 1995); APJS 106,213,1996)

IRON IONS: Fe I, II, III, IV, V

All C,N,O ions : Nahar and Pradhan, ApJS,
111, 3 39, 1997; Nahar, ApJS (1999).

See RECENT PUBLICATIONS - for all
references.

return to Anil K. Pradhan's home page

Revised: 1999 Dec. 1