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)


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

See RECENT PUBLICATIONS - for all references.

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Revised: 1999 Dec. 1