  Angle-resolved soft x-ray measurements made at the boron K-edge in single
crystal MgB2 provide new insights into the B-2p local partial density of both
unoccupied and occupied band states. The strong variation of absorption with
incident angle of exciting x-rays permits the clear separation of contributions
from \sigma states in the boron plane and \pi states normal to the plane. A
careful comparison with theory accurately determines the energy of selected
critical $k$ points in the conduction band. Resonant inelastic x-ray emission
at an incident angle of 15 degrees shows a large enhancement of the emission
spectra within about 0.5 eV of the Fermi level that is absent at 45 degrees and
is much reduced at 60 degrees. We conclude that momentum transferred from the
resonant inelastic x-ray scattering (RIXS) process couples empty and filled
states across the Fermi level.
