  We argue that the results proposed recently for the $\mathrm{a}^3\Sigma_u^+$
electronic state of $^7\mathrm{Li}_2$ do not exhibit any physical utility
because the canonical vibrational partition function for an excited electronic
state makes no sense according to the principles of statistical mechanics. Such
an approach may, in principle, be applied to the ground state of a diatomic
molecule. We show that the simpler model based on the harmonic oscillator and
rigid rotor enables one to derive a theoretical expression for the equilibrium
constant of a simple chemical reaction that agrees remarkably well with
experimental data. It is not clear whether the complicated formulas mentioned
above are suitable for any comparison with experimental data.
