Accessing tens-to-hundreds femtoseconds nuclear state lifetimes with low-energy binary heavy-ion reactions

TL;DR

This paper introduces a new Monte Carlo method for measuring nuclear state lifetimes in the tens to hundreds of femtoseconds range, validated with experiments involving neutron-rich nuclei and emphasizing the importance of gamma-tracking arrays for precise measurements.

Contribution

A novel Monte Carlo technique for lifetime determination in complex heavy-ion reactions, validated with experimental data and highlighting the role of gamma-tracking arrays for accuracy.

Findings

Validated the method with known lifetimes in $^{17}$O and $^{19}$O.

Demonstrated the importance of gamma-tracking arrays for precise Doppler correction.

Extended lifetime measurement capabilities to exotic neutron-rich nuclei.

Abstract

A novel Monte Carlo technique has been developed to determine lifetimes of excited states in the tens-to-hundreds femtoseconds range. The method is applied to low-energy heavy-ion binary reactions populating nuclei with complex velocity distributions. Its relevance is demonstrated in connection with the $^{18}$O(7.0 MeV/u) + $^{181}$Ta experiment, performed at GANIL with the AGATA+VAMOS+PARIS setup, to study neutron-rich O, C, N, ... nuclei. Excited states in $^{17}$O and $^{19}$O, with known lifetimes, are used to validate the method over the $\sim$20-400 fs lifetime-sensitivity range. Emphasis is given to the unprecedented position resolution provided by $\gamma$-tracking arrays, which turns out to be essential for reaching the required accuracy in Doppler-shift correction, at the basis of the detailed analysis of $\gamma$-ray lineshape and resulting state lifetime determination. The technique is anticipated to be an important tool for lifetime investigations in exotic neutron-rich nuclei, produced with intense ISOL-type beams.