The CHIANTI database
Adding Ionization and Recombination to
CHIANTI
Dr Peter Young
CCLRC/Rutherford Appleton Laboratory, UK
Dr Ken Dere
George Mason University, USA
Background
• Tables of ion fractions as a function of temperature are essential
for the analysis of electron-ionized plasmas
• In the past, rates have been re-assessed on timescales of ~5
years and new tables published
• Previous calculations include
The CHIANTI database
–
–
–
–
Mazzotta et al. (1998)
Arnaud & Raymond (1992)
Arnaud & Rothenflug (1985)
Shull & Van Steenberg (1982)
CHIANTI
• CHIANTI contains atomic data for the calculation of level
populations within ions
• Major updates occur every ≈ 2 years
The CHIANTI database
• There is no official CHIANTI ion fraction data-set
• The user can choose any of the standard ion fraction tables
CHIANTI version 6
• v.6 of CHIANTI will provide
The CHIANTI database
– ionization rates
– recombination rates
– ion fractions derived from these rates
Ionization
• Ionization rates have been assessed, and new calculations
performed for many ions
– K.P. Dere (2006, submitted to ApJ)
The CHIANTI database
• Experimental cross-section data have been fit with a Burgess &
Tully (1992) type fitting formula
f – scaling parameter; I – ionization potential; u = E/I; σ – cross-section
• High energy limit given by the Bethe coefficient
The CHIANTI database
Fitting the rates
• The ionization rate coefficients are also fit with a Burgess-Tully
type scaling
The CHIANTI database
f – scaling parameter; I – ionization potential; t = kT/I; σ – rate coefficient
• The spline fits to these scaled rates will be provided to the
CHIANTI user
Ionization: FAC calculations
• For many ions where experimental data are incomplete or
missing, new data have been calculated
• The Flexible Atomic Code (FAC) has been used
The CHIANTI database
– relativistic distorted wave code similar to that of Zhang & Sampson
(1991)
Example: Ni XIV
Radiative Recombination
• The baseline set of radiative recombination rates are derived from
fits embedded in a fortran routine of D.A. Verner
• Gives rates for all ions of all elements up to zinc
• These rates are used as the baseline, supplemented by
The CHIANTI database
– Badnell (2006)
– Wane & Aymar (1987)
– Aldrovandi & Pequignot (1974)
The CHIANTI database
Radiative Recombination Problems
The CHIANTI database
• Beyond the sodium sequence, most of the data have been
obtained by interpolation/extrapolation of the Woods et al. (1981)
data-set for the iron ions
• Comparisons with other data-sets show differences
Dielectronic recombination
• Baseline DR rates are taken from Mazzotta et al. (1998)
• New DR rates for all sequences up to the sodium sequence have
been calculated by N.R. Badnell and co-workers
The CHIANTI database
• Rates for Cu and Zn were not provided by Mazzotta et al. (1998).
These are taken from Mazzitelli & Mattioli (ADNDT, 2002)
The CHIANTI database
Comparison with Nahar data
• S. Nahar and colleagues have calculated combined RR and DR
rates for many ions
The CHIANTI database
• Significant differences exist for some ions for cases where new
Badnell data are available, and also where older data are being
used
The CHIANTI database
Blue curve: Badnell data
Red curve: Nahar data
The CHIANTI database
Blue curve: Mazzotta data
Red curve: Nahar data
New CHIANTI ion balance
The CHIANTI database
• Carbon ions
Conclusions
• Version 6 of CHIANTI should be ready in around 6 months
• For all ions of all elements up to zinc it will contain
The CHIANTI database
– ionization rates
– recombination rates
– ion fraction curves