Dickinson AS

Gadea FX

Leiniger T

Linewidths and shifts have been calculated in the impact approximation for atomic hydrogen broadening of the Na resonance and 3d-3p, 4d-3p and 5s-3p lines. The S-matrix elements required have been calculated in a time-dependent close-coupling approximation with straight-line paths for each Na term, including fine structure. The NaH potentials were determined using ab initio methods. Allowance was made for possible distant non-adiabatic transitions associated with ionic-covalent avoided crossings in 1Σ+ symmetry. Our result for the width of the resonance line at 5000 K is somewhat below the observed value, although the calculated shift coefficient is consistent with experiment. The shift coefficient for the 615.4 nm (5s-3p) lines is found to be comparable with the broadening coefficient, primarily due to unusual behaviour in the long-range 5s Σ+ potentials. The 819.4 nm (3d-3p) lines are found to have a larger broadening coefficient than the 568.8 nm (4d-3p) lines. For all the multiplets considered the different components of each line have widths differing by no more than a few per cent. Simple empirical fits are provided to the width coefficients of each multiplet

Broadening of the sodium 568.8, 589, 615.4 and 819.4 nm lines by atomic hydrogen

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