IR spectra of HF (a) and DF (b) in an Ar matrix. The spectra are measured at .
(a) Formation of HArF upon thermal annealing. In the upper trace (annealing at ), both unstable and stable configurations are present. In the lower trace (annealing at ), only the stable form is present.11,22 (b) Low-temperature formation of HArF and DArF.23 The upper trace is measured after at and the middle trace after at after photolysis. Notice that the unstable configuration of HArF is mainly formed at . The lower trace shows the situation after additional annealing of the matrix at . The band marked as is due to the librational motion of the HArF molecule in solid argon.21 The spectra are measured at . The HF(DF)/Ar matrix was preliminarily photolyzed with a Kr lamp. The photolysis-induced HArF absorptions are subtracted from the spectra shown in panel (b).
(a) Formation of unstable HArF as a function of time at different temperatures (8 and ). Formation of unstable DArF is shown at (down triangles) demonstrating a strong isotope effect. The spectra were measured at the annealing temperatures. The lines are stretched-exponential fits. (b) Demonstration of the negligible effect of IR light on the HArF formation at . The solid and open symbols present the data obtained with the closed and open Globar source between the measurements, respectively. The integrated absorbance was normalized by the value obtained after annealing at and the values after photolysis were subtracted. These experiments were done using relatively low HF concentrations .
(a) IR spectra of and . Spectrum I is obtained after irradiation. Spectra II and III represent the situations 8 and after photolysis. Spectrum IV is recorded after annealing the sample at . The spectra were measured at . (b) Decay of and in an Ar matrix at . The data were normalized by the values obtained after photolysis.
Arrhenius plot for the formation of unstable HArF and DArF and decay of . The unstable HArF and DArF formation time was estimated at 0.63 and 0.45 levels of the integrated intensity obtained after annealing at , respectively. The insert shows the HF-precursor concentration dependence of the HArF formation at . The ratios were estimated using the molar absorptivity of gaseous HF.29
Article metrics loading...
Full text loading...