The Collaborative International Dictionary of English v.0.48:

Deconcentrate \De`con*cen"trate\, v. t.
   To withdraw from concentration; to decentralize. [R.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

deconcentrate
    v 1: make less central; "After the revolution, food distribution
         was decentralized" [syn: decentralize, deconcentrate,
         decentralise] [ant: centralise, centralize,
         concentrate]