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Compilation and evaluation of atomic data is carried out at several locations listed below. Apart from astronomy, perhaps the largest user of atomic data is the nuclear fusion community which is served by some of these data centers.

The latest version 0.7 of TOPBASE may be accessed from two nodes:

Some of the TOPBASE data is being upgraded through new calculations by the Iron Project, in particular for the important low ionization stages of Iron (Fe I - V). The photoionization cross sections obtained using the low energy close coupling approximation with the R-matrix method, and incorporated in TOPBASE, are of high accuracy in the important near-threshold region containing the extensive autoionizing resonance structures. However, in the high energy region the cross sections are often inaccurate owing to the presence of pseudo resonances. Thus the TOPBASE photoionization cross sections were fitted to a simple nu-3 ``tail'' above all thresholds of ionization included in the close coupling calculations; these are not reliable for applications that need such data (e.g. X-ray opacities that involve inner-shell ionizations). A new effort is under way to improve the high energy ``tails'' of the photoionization cross sections and will be incorporated into TOPBASE in due course.

Further extensions of TOPBASE are also planned to include collisional data from the Iron Project (TIPBASE), as well as data for electron-ion recombination rate coefficients.

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