Knowledge Bank

Simulation of carbon dioxide spectra at temperatures up to 1500K requires higher vibrational levels, and line positions to much higher angular momentum quantum number J, than have been observed. Direct Numerical Diagonalization (DND)$\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}$ allows extrapolation to such high vibrational levels and high J, but does not reproduce observed lower-J line positions to within experimental accuracy. For the HITEMP line parameter compilation, we chose to fit spectroscopic constants $Gv,Bv.Dv,Hv,Lv$, and $Pv$, to the observed line positions, and to high-J DND-calculated line positions, simultaneously. This allows smooth extrapolation while preserving a good fit to the observed positions. Examples of bands fitted in this way, and the quality of fit to be expected in HITEMP, will be presented.