Figure 1

Energy conditions for various nuclear decay modes: (a) true two-nucleon, (b) true four-nucleon, (c) sequential $\left(2N\right)$-$\left(2N\right)$ emission with the example of ${}^8$C decay. $S_{kN}$ is separation energy of $k$ nucleons. For the decay scheme of ${}^8$C spin parities $J^{\pi }$, decay energies $E_T$, and widths $\Gamma$ (in MeV) are indicated.Reuse & Permissions

Figure 2

Estimated widths for (a) one-nucleon, (b) true two-nucleon, (c) true $4n$ emission calculated for different orbital configurations. In the case of neutron emission, the low-energy behavior of the widths has an asymptotic dependence $\sim E_T^{\alpha }$, as is indicated next to the corresponding curves. The hatched area indicates the lifetime range accessible by decay-in-flight techniques. The results for ${}^{26}$S from Ref. [9] are represented in panel (b) by the thick dots. The dash-dotted curve in panel (c) provides the estimate of the sequential $\left(2n\right)$-$\left(2n\right)$ decay of ${}^{28}$O via ${}^{26}$O g.s., whose decay energy is 20 keV.Reuse & Permissions

Figure 3

Schematic view of a suggested setup for experimental studies of long-lived neutron emitters by tracking their decay products in flight. The high-resolution neutron detector HRND is combined with a charged-particle detector for tracking the heavy fragments also with high angular resolution.Reuse & Permissions

Figure 4

Monte Carlo simulations of the angular distributions between the heavy fragment and one of the neutrons for decay energies of 20 keV (solid curves) and 300 keV (dashed curves): (a) spectra for the true $2n$ decay of ${}^{26}$O; (b) spectra for the true $4n$ decay of ${}^{28}$O. The dash-dotted curve in (b) refers to a sequential $2n$-$2n$ decay of ${}^{28}$O via the ${}^{26}$O g.s. with $4n$- and $2n$- decay energies of 300 and 20 keV, respectively.Reuse & Permissions