blike_jl96#fe21j.dat

• Spontaneous Emission: Fe⁺²¹(i) → Fe⁺²¹(j) + hv
• Electron Impact Excitation: Fe⁺²¹(i) + e → Fe⁺²¹(j) + e

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 ENERGY LEVELS AND IONISATION POTENTIAL
 The ionisation potential is from Kelly (J Phys Chem Ref Data 16, 
 Suppl 1, 1987). The energies are from Sugar J and Rowan W L
 (Journal of the Optical Society of America B, 12, 1403, 1995) for
 levels 2s2 2p and 2s 2p2 and from Edlen (Phys Scripta 28, 483, 
 1983) for levels 2p3. The ordering of the levels is as given in the 
 work used for the effective collision strengths. There are differences 
 in energy of up to 323 cm-1 with the data from the NIST discs.

 TRANSITION PROBABILITIES
 For the transition between the 1/2 and 3/2 levels of the ground term 
 the multiconfiguration Hartree-Fock Breit-Pauli result of C Froese 
 Fischer (J Phys B 16, 157 1983) is used (1.53+04 s-1). The
 multiconfiguration Dirac-Fock calculations of Cheng, Kim and 
 Desclaux (ADNDT 24, 111, 1979) yielded 1.48+04 s-1 while Bhatia,
 Feldman and Seely (ADNDT 35, 319, 1986) gave 1.47+04 s-1.

 The results of of Merkelis, Vilkas, Gaigalas and Kisielius were 
 adopted (Phys Scripta 51, 233, 1995). Their calculation employed 
 the stationary second order many-body perturbation theory, the 
 relativistic corrections being included using the Breit-Pauli 
 approximation. Results for this ion using the multiconfiguration 
 Hartree-Fock with Breit-Pauli correction have been published by
 Dankwort and Trefftz (Astron Astrophys 65, 93, 1978) who did not
 give results for transitions involving 2p3 levels for this ion.
 For allowed E1 transitions the results of Merkelis et al obtained
 in intermediate LSJ-coupling are close to those determined by 
 Dankwort and Trefftz and Cheng et al. In fact Bhatia et al gave
 very similar results to both Merkelis et al and Cheng et al. The
 2-8 transition shows a wide range of values.

 EFFECTIVE COLLISION STRENGTHS
 In their assessment of effective collision strengths for the B-like 
 sequence Sampson, Zhang and Fontes (ADNDT 57, 98, 1994) review the 
 available results. No close coupling results were then available
 for this ion. However, Sampson et al anticipated the R-matrix close
 coupling calculations of Zhang, Graziana and Pradhan (Astron 
 Astrophys 283, 319,1994) for the 105 fine structure transitions 
 among the 15 levels of the 2s2 2p, 2s 2p2 and 2p3 configurations.
 These results are adopted here. The data were obtained 
 electronically and processed into ADF04 format.
 Zhang and Pradhan (Phys Rev A 50, 3105, 1994) point out that 
 preliminary results from a Breit-Pauli R-matrix calculation for this
 ion show that including relativistic effects with the term coupling
 coefficients, as was done by Zhang, Graziana and Pradhan, may not 
 fully account for relativistic effects. They indicate that the 
 Breit-Pauli work is in progress.
  

 J Lang
 A Lanzafame         April 1996
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Contributors

• Jim Lang
• Hong Zhang
• Douglas Sampson
• Alessandro Lanzafame