Decay of thermally emitted n-p states: A means to measure their lifetime

The evaporation and subsequent decay of n-p states (especially H*2-the singlet deuteron) from compound nuclei is examined theoretically. The energy difference between a proton and neutron observed in coincidence provides information about the time interval between the thermal emission and the breakup of the n-p state. It thus offers the opportunity for measuring a lifetime of the order of 10-21 seconds, without recourse to the relation Δt=Latin small letter h with stroke/Γ. Thermal emission of both singlet and triplet deuterons is considered. The subsequent decay through the natural mode and polarization mode is calculated. Results of Monte Carlo calculations are presented for both coincidence and singles spectra, and the feasibility of direct lifetime measurement is discussed.