The production of deuterons and antideuterons in the transverse momentum range 1:1NN=200GeV has been studied by the PHENIX experiment at RHIC. A coalescence analysis, comparing the deuteron and antideuteron spectra with that of proton and antiproton, has been performed. The coalescence probability is equal for both deuterons and antideuterons and it increases as a function of pr, which is consistent with an expanding collision zone. Comparing (anti)proton yields, p/p=0:73±0:01, with (anti)deuteron yields,d/d=0:47±0:03, we estimate that n/n=0:64±0:04. The nucleon phase space density is estimated from the coalescence measurement