The linelist format used by the Belfast line formation code SPECTRUM is a convenient means of storing atomic data needed for LTE line formation calculations. A substantial amount of data of varying quality is available in the literature. This database aims to maintain 'recommended' values for various atomic data, alongside information on sources, in a uniform manner. It does not necessarily contain the 'best' data, although this is a long term aim.
Atomic data for transitions in specific ions are stored in individual files (e.g. He1.d, C1.d, C2.d, .... ). The individual line data include atom and ion identifiers, wavelength, oscillator strength, electron and radiative damping constants, excitation potential of the lower level in a transition, a multiplet identifier, and reference codes. The dataare currently given in the following format.
Atom wavelength log electron radiative van der exc. multiplet references Ion (A) gf-value damping damping Waal's pot. (Moore) 0 0 0000.000 0.000 +00.000 +00.000 +00.000 0.000 00.00 OSC/EDAMP/RDAMP/VDW Column Explanation Example 1 Atomic number 6 Carbon 2 Ionisation stage 2 Singly ionised 3 Wavelength (Angstroms) Moo 48, etc. 4267.2 4 Oscillator strength log gf 5 Electron damping width: log Gamma_e 6 Radiative damping width: log Gamma_r 7 Van der Waal's damping width: log Gamma_r 8 Excitation energy of lower level (electron Volts) 9 Multiplet identification Moo 48, etc 10 References for 4 -- 7
Where there is more than one entry for a given line, the recommended entry is entered normally. Other entries are preceded by a minus sign in the atomic identifier field. This is to preserve old data in the database.
Many damping constants are obtained from classical approximation formulae: these are indicated by a dash in the column for references. Where not even this level of sophistication is achieved, an approximate value may have been entered. No reference is cited, and fewer significant figures are placed in the table. A substantial effort is still required to extend the damping constant data.