Knowledge Bank

To calculate high-J fine-structure lines in fundamental bands of spherical tope, one can usually replace the diagonalization of the Hamiltonian by a second- or third-order approximation. The new formalism uses an expansion in powers and products of the diagonal $F(4)$ - and $F(6)$ - coefficients of Moret-$Bailly.1$ The fit to diode spectra attains about the same accuracy as the analysis that incorporates diagonalization, and the sets of derived parameters agree closely in value. Results will be discussed for the fundamental bands of $SiF4$, where the theory converges rapidly for the $\nu 3$ band and more slowly for the $\nu 4$ band. $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}$J. Moret-Bailly, J. Mol. Spectrose. 15, 344-354 (1965).