Short-range Lifetime Measurements for Deep-inelastic Reaction Products: the ¹⁹O Test Case

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.