Experimental and computational study of neutral xenon halides (XeX) in the gas phase for X=F, Cl, Br, and I

We report a combined experimental and theoretical study of the xenon monohalide radicals XeX• (X=F, Cl, Br, and I) together with their cationic and anionic counterparts XeX+ and XeX−. In brief, the XeX+ cations are characterized by reasonably strong chemical bonds with significant charge-transfer stabilization, except for X=F. In contrast, the neutral XeX• radicals as well as the XeX− anions can mostly be described in terms of van der Waals complexes and exhibit bond strengths of only a few tenths of an electron volt. For both XeX• and XeX− the fluorides (X=F) are the most strongly bound among the xenon halides due to significant covalency in the neutral radical, and to the large charge density on fluoride in the XeX− anion, respectively. Mass spectrometric experiments reveal the different behavior of xenon fluoride as compared to the other halides, and in kiloelectron-volt collisions sequential electron transfer according to XeX+→XeX•→XeX− can be achieved allowing one to generate neutral XeX• radicals with lifetimes of at least a few microseconds for X=F and I.