Knowledge Bank

Samples of the methylene halides in argon have been subjected to radiolysis during condensation on a cold window, by a beam of 2 keV protons. Spectra of these samples indicate that the major products are the $CHX2$ radical and the $CHX2+$ cation in the $CHX2+(X-)$ ion pair. In addition, a single new band of medium intensity was observed in each experiment, $20-25cm-1$ above the carbon-halogen stretching band of the parent molecule, and the new band readily photobleached. Also, this new band was the only product of the vacuum ultraviolet photolysis of similar $Ar/CH2X2$ samples, using 1048 {\AA} and 1067 {\AA} light from an argon discharge. The chemical composition of the new species, and the known photoionization threshold of the methylene halides strongly suggests the assignment of this band to the isolated $CH2X2+$ species.