* Infrared spectroscopy: the C=O double bond absorbs infrared light at wavenumbers between approximately 1600&ndash;1900 cm(5263 nm to 6250 nm). The exact location of the absorption is well understood with respect to the geometry of the molecule. This absorption is known as the "carbonyl stretch" when displayed on an infrared absorption spectrum. In addition, the ultraviolet-visible spectra of propanone in water gives an absorption of carbonyl at 257 nm.
* Nuclear magnetic resonance: the C=O double-bond exhibits different resonances depending on surrounding atoms, generally a downfield shift.  The C NMR of a carbonyl carbon is in the range of 160–220 ppm.