  Previously-determined empirical energy levels are used to construct a
rovibronic model for the $\mathrm{X}\,^4\Sigma^-$, $\mathrm{A}'\,^4\Phi$,
$\mathrm{A}\,^4\Pi$, $\mathrm{B}\,^4\Pi$, $\mathrm{C}\,^4\Sigma^-$,
$\mathrm{D}\,^4\Delta$, $\mathrm{1}\,^2\Delta$, $\mathrm{1}\,^2\Sigma^+$,
$\mathrm{1}\,^2\Phi$, $\mathrm{1}\,^2\Pi$ and $\mathrm{2}\,^2\Pi$ electronic
states of vanadium mononoxide. The spectrum of VO is characterized by many
couplings and crossings between the states associated with these curves. The
model is based on the use of potential energy curves, represented as extended
Morse oscillators, and couplings (spin-orbit, spin-spin, angular momentum),
represented by polynomials, which are tuned to the data plus an empirical
allowance for spin-rotation couplings. The curves are used as input for the
variational nuclear motion code \duo. For the $\mathrm{X}\,^4\Sigma^-$,
$\mathrm{1}\,^2\Phi$ and $\mathrm{1}\,^2\Pi$ states the model reproduces the
observed energy to significantly better than 0.1 $\mathrm{cm}^{-1}$. For the
other states the standard deviations are between 0.25 and 1.5
$\mathrm{cm}^{-1}$. Further experimental data and consideration of hyperfine
effects would probably be needed to significantly improve this situation.
