sentences:  Case described the detector material as consisting of thallium, oxygen and sulfur, and this was incorrectly described by others as being thallium oxysulfide, which incidentally is a compound that is not known.Case's work was then built on by R.J. Cashman who recognised that the controlled oxidation of the Tl2S film was key to the operation of the cell.Cashman's work culminated in the development of long wave infrared detectors used during the Second World War.