Short-range Lifetime Measurements for Deep-inelastic Reaction Products: the $^{19}$O Test Case
Résumé
An experiment, aiming at measuring lifetimes of excited states in neutron-rich C and O isotopes, was performed at the GANIL laboratory with the use of the AGATA segmented HPGe tracking array, coupled to the PARIS scintillator array and to the VAMOS++ magnetic spectrometer. The nuclei of interest were populated in transfer and deep-inelastic processes induced by an 18O beam at 126 MeV (7.0 MeV/u) on a 181Ta target. This paper contains a brief description of a novel implementation of a Monte-Carlo technique, which allowed us to obtain excited states lifetimes in the range from tens to hundreds femtoseconds for a reaction with complex initial velocity distribution, making use of the Doppler-shift attenuation method (DSAM). As a test case, we present here the analysis for two states in 19O: 2371-keV 9/2 + and 2779-keV 7/2 +, for which lifetimes of τ > 400 fs and τ = 140+50 −40 fs were obtained, respectively, in agreement with literature values. This newly developed approach will be essential for short lifetimes measurements in neutron-rich systems, exploiting intense ISOL-type beams, currently under development.
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