  It is believed that the D1D5 brane system is described by an 'orbifold CFT'
at a special point in moduli space. We first develop a general formulation
relating amplitudes in a d-dimensional CFT to absorption/emission of quanta
from flat infinity. We then construct the D1D5 vertex operators for minimally
coupled scalars in supergravity, and use these to compute the CFT amplitude for
emission from a state carrying a single excitation. Using spectral flow we
relate this process to one where we have emission from a highly excited initial
state. In each case the radiation rate is found to agree with the radiation
found in the gravity dual.
