High-resolution Fourier-transform infrared spectroscopy of the v 3(F2) fundamental of RuO4

The v 3(F2) fundamental band of ruthenium tetroxide (RuO4) vapour is investigated by high-resolution (0·004 cm-1 FWHM) interferometric FTIR spectroscopy in the range 850-1000 cm-1. The rotational fine structure is largely resolved and accurately analysed on the basis of third- and fourth-order (diagonal) effective Hamiltonians in the theory of Moret-Bailly. The analysis of the enriched isotopomer spectra gives m = 921·6514 cm-1 (102RuO4) and m = 920·0674 cm-1 (104RuO4). Many other constants for these are summarized in tables. For other isotopomers we find m(96) = 926d83 cm-1, m (99) = 924·14 cm-1, m(100) = 923·31 cm-1 and m(101) = 922·46 cm-1 from an approximate analysis of the spectrum of the natural isotope mixture. Many coincidences of rovibrational transitions in RuO4 with N2O and CO2 laser lines are predicted and assigned. The importance of the results for sub-Doppler spectroscopy, IR-laser isotope separation and the analysis of symmetry (and parity) selection rules is discussed briefly.