Vibrational–rotational spectra of GaF and global multi-isotopologue analysis

Abstract

In total, 521 vibrational–rotational spectral lines of the Δv=1 transitions of 69GaF and 71GaF up to bands v=5–4 and 4–3, respectively, were recorded in emission with a Fourier-transform spectrometer at unapodized resolution 0.010cm−1 in range 625–660cm−1. The response of a HgCdTe detector enforced the lower limit, 625cm−1. To calibrate accurately the spectral lines, the absorption spectrum of CO2 was simultaneously recorded, using dual sample cells, to serve as wavenumber standards. A set of 782 spectral lines comprising all present vibrational–rotational spectra of 69GaF and 71GaF, the reported laser-diode measurements of the Δv=1 band sequence and the reported rotational spectra was subjected to a global multi-isotopologue analysis through fitting with 11 isotopically invariant, irreducible molecular parameters in a single set. Normalized standard deviation 1.093 indicates a satisfactory fit. For the effects of the breakdown of the Born–Oppenheimer approximation on GaF, the values of non-Born–Oppenheimer parameters ΔBGa, ΔωGa and r1qGa(=r1qF) are experimentally determined for the first time. To facilitate the calculations or predictions of spectral frequencies, the values of the Dunham coefficients of 24 Yij and 81 band parameters for both 69GaF and 71GaF were back-calculated with uncertainties using the 11 evaluated molecular parameters. To date, various types of effective Be, re, ωe, and k have been reported for GaF. Because, in the present work, Dunham coefficients Yij are algebraically expressed with the genuine Be, ωe, ai (i=1, …) and the non-Born−Oppenheimer correction parameters, the exact expressions for the physical significance of effective quantities are derivable. The various effective quantities of Be, re, ωe and k calculated with these expressions for the physical significance and the determined values of the fitted parameters of GaF agree satisfactorily with the reported values. The physical significance of the conventional treatments of adiabatic and nonadiabatic corrections for Δ01Ga and Δ10Ga is discussed.