The solvation dynamics of an ammonia molecule seeded into a droplet of He-4 containing N = 1-25 He-4 atoms are studied using the diffusion Monte Carlo method. Excited states are computed using the fixed-node procedure. The reduction of similar to 3-5% in the rotational constants of the molecule is in quantitative agreement with recent experiments of Slipchenko and Vilesov (2005) [26] and disagrees with the much larger similar to 25% reduction originally reported by Behrens et al. (1998) [25]. (C) 2010 Elsevier B.V. All rights reserved.