 Hydrogen iodide: Constants of diatomic molecules by Klaus P. Huber and others

By Klaus P. Huber and Gerhard H. Herzberg. NIST Chemistry WebBook compilation of diatomic constants.

Cited row: ground $X{}^1{\Sigma }^{+}$ state of hydrogen iodide, ${\omega }_e=2309.014\mathrm{c}{\mathrm{m}}^{-1}$ and ${\omega }_e{x}_e=39.6435\mathrm{c}{\mathrm{m}}^{-1}$. Higher anharmonic coefficients are also tabulated, so the two-constant Morse oscillator extrapolation should not be confused with a measurement of the actual dissociation threshold.