FTIR spectra of the HFminus;2and H2Fminus;3anions isolated in solid argon and neon

摘要

Argon diluted samples of HF were bombarded by low energy electrons (150ndash;400 eV) from a thermionic electron source during condensation at 12 K. Several polyfluoride anions, which have extremely strong hydrogen bonds, were characterized using matrix infrared spectroscopy. Three principal ions were trapped in the argon matrix: HFminus;2(1377 cmminus;1), H2Fminus;3(1815 cmminus;1), and ArnH+(904 cmminus;1). Electron impact experiments performed with HF/DF mixtures gave counterpart absorptions: DFminus;2(965 cmminus;1), HDFminus;3(1707 cmminus;1), D2Fminus;3(1391 cmminus;1), and ArnD+(644 cmminus;1). The 1377 cmminus;1matrix band is assigned to ngr;3of linear, centrosymmetric HFminus;2, based on agreement with solid state and matrix ion pair spectra, andabinitiocalculations, and a proper H/D ratio (1.427) for a linear centrosymmetric species. However, this assignment challenges the recent 1848 cmminus;1gas phase assignment to ngr;3of HFminus;2using laser spectroscopy; the 1848 cmminus;1absorption exhibits an H/D ratio (1.323) that is too low for the ngr;3vibration of centrosymmetric HFminus;2, and it should be reassigned to the ngr;1+ngr;3combination band. The 1815 cmminus;1matrix band is assigned to the outhyphen;ofhyphen;phase Hndash;F stretching fundamental ofC2vH2Fminus;3, which is in agreement with solid K+H2Fminus;3spectra.