Line identification is one of the basic operations in stellar spectroscopy, which aims at determining the element responsible for each observed spectral line.

The process of identification is based upon

1. (a) measurement of accurate wavelengths of the lines,

2. (b) measurements of the intensity of the lines (or line intensity estimates on a personal scale) and

3. (c) use of line identification tables.

With modern detectors and reduction techniques points (a) and (b) offer no great difficulty, if carried out on adequate observational material – i.e. small plate factors, high resolving power and high signal-to-noise ratio. We should mention an important point concerning the resolving power of the spectrograph, namely that one can only see as separate features two lines that are more separated than the resolving power. The latter is usually fixed by the size of the photographic grain or the pixel size and is normally much larger than the accuracy with which one can measure the position of the barycenter of the (unresolved) line.

On the other hand, point (c) presents a certain number of problems. Very often identifications start with use of the classical paper ‘A multiplet table of astrophysical interest’ (Moore 1945). Such a practice leaves out all laboratory work that has been done since then and that often represents a considerable improvement over Miss Moore's tables. The fact that most of this recent work is not used by astrophysicists is due to the absence of an updated version of wavelength tables, arranged in a similar way to that of Moore. The following compilations are available.