Permission given by Jonathan Friedman to User:Rmrfstar to release under the GFDL on 9/21/06. The details of the diagram as given by Dr. Friedman in an email to Rmrfstar:

As the title states, it is the transmission function for potassium at the D1 transition at 770.1093 nm (vacuum). The axial magnetic field is 1320 Ga and the cell temperature is 113.6 C. The fact that the normalized transmission maximum is only 0.5 is because it is for a single polarization. No optical losses are included. The pink area in the center corresponds to the commonly used transmission region of the filter. The abscissa is in wavelength, centered at 770.1093 nm. If you wanted it in frequency, the conversion to GHz is 50 GHz/angstrom, and in wavenumbers it is 1.67 cm⁻¹ per angstrom.

This graph image could be re-created using vector graphics as an SVG file. This has several advantages; see Commons:Media for cleanup for more information. If an SVG form of this image is available, please upload it and afterwards replace this template with {{vector version available|new image name}}. It is recommended to name the SVG file “K-FADOF-spectrum.svg”—then the template Vector version available (or Vva) does not need the new image name parameter.

This graph image was uploaded in the JPEG format even though it consists of non-photographic data. This information could be stored more efficiently or accurately in the PNG or SVG format. If possible, please upload a PNG or SVG version of this image without compression artifacts, derived from a non-JPEG source (or with existing artifacts removed). After doing so, please tag the JPEG version with {{Superseded|NewImage.ext}} and remove this tag. This tag should not be applied to photographs or scans. If this image is a diagram or other image suitable for vectorisation, please tag this image with {{Convert to SVG}} instead of {{BadJPEG}}. If not suitable for vectorisation, use {{Convert to PNG}}. For more information, see {{BadJPEG}}.