  Annihilation momentum densities and correlation enhancement factors for
low-energy positron annihilation on valence and core electrons of noble-gas
atoms are calculated using many-body theory. s, p and d-wave positrons of
momenta up to the positronium-formation threshold of the atom are considered.
The enhancement factors parametrize the effects of short-range
electron-positron correlations which increase the annihilation probability
beyond the independent-particle approximation. For all positron partial waves
and electron subshells, the enhancement factors are found to be relatively
insensitive to the positron momentum. The enhancement factors for the core
electron orbitals are also independent of the positron angular momentum. The
largest enhancement factor ($\sim 15$) is found for the 5p orbital in Xe, while
the values for the core orbitals are typically $\sim 1.5$.

Atomic Physics