Cryospectroscopic analysis of individual xenon fluorides

Abstract

Considerable attention has been paid lately to pure fluorination agents, in particular xenon fluorides, which are usually produced as a result of interaction of high purity xenon and fluorine activated thermally, photochemically, plasmochemically or by other methods. However, the production of individual xenon fluorides is somewhat difficult because as a rule a mixture of XeF 2, XeF 4 and XeF 6 usually forms in the reactor. Moreover, whereas the choice of the optimal conditions of synthesis yields practically pure XeF 2 and XeF 6, a small quantity (10 −2–10 −3 mol. part) of XeF 2 and XeF 6 impurities forms during XeF 4 production, even under optimal conditions. Thus it is necessary to control the composition of synthesized fluorides XeF n ( n=2, 4, 6) directly in the reaction zone. IR spectroscopy of XeF 4 solutions in liquid xenon at T=180 K was used to solve this problem. Spectra registration was carried out in the range 700–500 cm −1 (L cryo=10 cm). In xenon fluorides spectra the bands of fundamental modes ν 3(XeF 2)=544.7 cm −1, ν 6(XeF 4)=571.8 cm −1, ν(XeF 6)=596 cm −1 were registered and identified. Measurement of the xenon fluorides solubility in liquid xenon gave the following results: XeF 2=1.4·10 −5 mol/l, XeF 4=6·10 −6 mol/l, XeF 6=4·10 −4 mol/l. The study of XeF n infrared spectra in the region of fundamental modes showed that their main bands are distant (Δν≊25 cm −1) with half-width Δν 1 2 ≊5–6 cm −1. Therefore, there is a real possibility of carrying out quantitative analysis for the presence of other xenon fluorides in individual XeF n . Estimation showed that the use of a cryostat with an optical length of 50–100 cm gives the possibility to detect the impurities of xenon fluorides in individual form of XeF n in quantities 10 −3–10 −5 mol. part.