Abstract
Molecular dynamics simulation of slowing down of nuclei produced in thermal neutron capture reactions is used to deduce lifetime values of excited nuclear states in 36 Cl[τ=63±2 fs (E x=1.959 MeV) , 48±26 (2.49), 31±5 (2.68), 21±1 (2.86), 59±3 (3.60)], 49 Ti[29±2 (1.76), 79±4 (3.18), 16.2±0.7 (3.26)] , 54 Cr [112±22 (2.62), 10.3±0.5 (3.07), 24±2 (3.72)], 57 Fe [52±4 (1.63), 38±3 (1.73)] , 59 Ni [40±7 (2.89), 37±5 (3.18), 6.5±1.4 (4.14)], and 61 Ni [73±14 (2.12)] from Doppler-broadened γ-ray line shapes. It is characteristic for the line shapes that they are produced by emission of secondary γ-rays from nuclei recoiling at ultra-low velocities, below 10 5 m/s, the recoil energy being imparted to nuclei by emission of typically 5–10 MeV primary γ-rays. The novel method of analysis used in the deduction of the lifetime values is described. The relevance of interatomic potentials on the reliability of lifetime values is considered.
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