Loomis-Wood plot

Bandheads are prominent features of a Loomis-Wood plot. A family of straight and curved lines emanates from the bandhead of the mapped branch on the Loomis-Wood plot. The straight lines actually intersect at the bandhead and correspond to various orders of the mapped branch. The curved lines are generated e.g. when the post-head R-branch overlaps with the pre-head segment of itself or with the P-branch described by the same Fortrat equation. Another prominent feature of Loomis-Wood plots is a horizontal strip free of points, which surrounds the mapped branch. The width of this strip is determined by the widths of lines in the mapped branch (instrumental resolution, Doppler width, nonradiative decay width, or unresolved hyperfine splittings). The Loomis-Wood plot can provide a survey map of J-dependent linewidth variations that encode valuable information about unimolecular dynamics. 

Figure 1.7c A one-sided (U-branch region only) Loomis-Wood plot of a not yet analyzed band of 181TaO in the 9900-10130 cm-1 region, with a vertical span of 2 cm-1. The 8 horizontal lines correspond to the 8 expected A J = AF hyperfine components for a nuclear spin of / = 7/2 21+1 = 8) (from Al-Khalili, et al., 1999).

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