  The temperature ($T$) dependent metal-insulator transition (MIT) in VO$_2$ is
investigated using bulk sensitive hard x-ray ($\sim$ 8 keV) valence band, core
level, and V 2$p-3d$ resonant photoemission spectroscopy (PES). The valence
band and core level spectra are compared with full-multiplet cluster model
calculations including a coherent screening channel. Across the MIT, V 3$d$
spectral weight transfer from the coherent ($d^1\underbar{\it {C}}$ final)
states at Fermi level to the incoherent ($d^{0}+d^1\underbar{\it {L}}$ final)
states, corresponding to the lower Hubbard band, lead to gap-formation. The
spectral shape changes in V 1$s$ and V 2$p$ core levels as well as the valence
band are nicely reproduced from a cluster model calculations, providing
electronic structure parameters. Resonant-PES finds that the
$d^1\underbar{\it{L}}$ states resonate across the V 2$p-3d$ threshold in
addition to the $d^{0}$ and $d^1\underbar{\it {C}}$ states. The results support
a Mott-Hubbard transition picture for the first order MIT in VO$_2$.
