The use of neat fluorine in matrix isolation is reported, as well as the formation of polyfluoride monoanions under cryogenic conditions. Purification procedures and spectroscopic data of fluorine are described, and matrix shifts of selected molecules and impurities in solid fluorine are compared to those of common matrix gases (Ar, Kr, N₂, Ne). The reaction of neat fluorine and IR‐laser ablated metal atoms to yield fluorides of chromium (CrF₅), palladium (PdF₂), gold (AuF₅), and praseodymium (PrF₄) has been investigated. The fluorides have been characterized in solid fluorine by IR spectroscopy at 5 K. Also the fluorination of Kr and the photo‐dismutation of XeO₄ have been studied by using IR spectroscopy in neat fluorine. Formation of the [F₅]⁻ ion was obtained by IR‐laser ablation of platinum in the presence of fluorine and proven in a Ne matrix at 5 K by two characteristic vibrational bands of [F₅]⁻ at 850.7 and 1805.0 cm⁻¹ and its photo‐behavior.