Knowledge Bank

Theoretical studies are reported of high-temperature ($T\approx 1,800\circ K$) inert-gas-buffered Li/$Li2$ vapor absorption cross sections in support of concomitant transmission measurements over the visible spectral region. Particular attention is addressed to the Li resonance doublet and to the X $\to$ A, B bands of $Li2$. Excitation of high rotational states ($Jmax$ $\approx$ 30) necessitates careful treatment of non-rigid rotor effects and the general J-dependence of absorption strengths. Voigt lineshapes and appropriate pressure widths (P $\approx$ 1 atm.) are employed in construction of rotationally resolved absolute cross sections for comparison with and interpretation of the measured spectra. Comments are provided on the possible presence of $Li2$ triplet contributions to the spectra, on the identification of absorption features due to trace contaminants, verification of Li/$Li2$ equation-of-state data, and on the ab initio procedures employed in the calculations.