We have studied the metal-insulator (MI) transition in VO2 with angle
resolved x-ray absorption spectroscopy. Above T-MI the oxygen K near e
dge structure shows two resolved peaks, the intensities of which do no
t change if the polarization vector (E) under bar is rotated within th
e rutile (ab) plane, but vary by a factor of two when (E) under bar is
rotated in the (ac) plane. Below T-Mf we observe a third peak which s
hows strong angular dependence: it vanishes for (E) under bar perpendi
cular to <(c)under bar(not)> and is largest for (E) under bar parallel
to <(c)under bar(not)>, confirming earlier suggestions that this peak
is due to the so called d parallel to band. We find analogous feature
s in the M-2 and T phases of Cr doped VO2. From comparisons of these s
pectra we conclude that shifts in the d parallel to band between the i
nsulating and metallic phase are primarily due to the effect of correl
ations and the other shifts to the formation of dimers; tilting of the
dimers plays only a minor role.