Experimental Search for the Singlet Metastable Deuteron in the Radiative n-p Capture

We performed an experimental search for the bound state singlet deuteron predicted in some microscopic calculations. The experiment consists in a high statistics measurement of gamma ray spectra after thermal neutron capture by hydrogen nuclei. The upper limit is obtained for the probability of the 3S1 - 1S0 -transition population of the deuteron singlet bound state with the bound energy in the interval 25-125 keV.