The UV photodesorption (6.4 eV) of ammonia from Cu(111) has been investigated using resonance enhanced multiphoton ionization through the (B) over tilde <-- (X) over tilde transition for state specific detection. We have measured the relative populations of both inversion doublet states of the first three vibrational levels in the nu(2), mode and the rotational excitation of photodesorbed NH3. The average energy content in the nu(2) mode corresponds to a temperature of T-nu 2 = 1000 K which is significantly larger than the translational energy released normal to the surface [E(trans)]/2k = 600 K. A marked underpopulation of the antisymmetric nu(2) levels has been observed. The rotations can be described by a Boltzmann distribution with a temperature close to the surface temperature indicating that the molecules do not experience significant torque during the desorption process. No pronounced correlation effects in the population of different degrees of freedom are found. These experimental results are consistent with the assumption that the energy required for desorption is transferred from the initial electronic excitation to the molecule-surface bond via the intramolecular coordinate nu(2).