Speaker
Description
Beta-decaying, spin-trap isomers have been observed in $^{96}$Y, $^{98}$Y and $^{100}$Y with half-lives ranging from 9 to 0.7 seconds [Ab08,Ch20,Si21]. A recent paper [Ca25] has investigated the isomeric-yield ratio in production of all three in fission and observed that, in $^{96}$Y and $^{100}$Y it is the higher-spin state which is populated more strongly, whereas in $^{98}$Y the opposite situation is observed. Moreover, Cannarozzo et al., [Ca25] concluded that in $^{100}$Y the higher-spin state is the ground state which is opposite to the ordering in [Si21]. In $^{102}$Y there are two beta-decaying states which have similar half lives (t$_{1/2}$ = 360(40) ms [Sh83] and 300(10) ms [Hi91]) and a small energy difference, making it difficult to measure their relative energy. Data measured at the JOSEF recoil separator at Jülich [Sh83] indicates that it is the high-spin state that is preferentially populated in the thermal fission of $^{235}$U but it is still unknown whether this is the ground- or isomeric state.
This presentation will report on the use of the Phase Imaging – Ion cyclotron Resonance (PI-ICR) method [El13] at the JYFLTRAP double Penning trap at the IGISOL facility at the University of Jyväskylä, Finland to measure the relative energies of the beta-decaying states in $^{102}$Y and re-measure $^{100}$Y. The nuclei of interest were produced via induced fission of $^{238}$U using a 30 MeV proton beam. In $^{100}$Y a value of 147.8(42) keV was measured for the excitation energy of the isomeric state, which overlaps with the previously measured value of 145(15) keV [Ha07] and reduces the experimental error by a factor of 4. In $^{102}$Y the closeness in energy of the 2 states makes the analysis quite complicated and although the two states were not fully separated, the observed mass distribution can be fitted with a bi-modal distribution with preliminary analysis indicating an excitation energy of ~10 keV for the isomeric state. Details of the experiment and of the analysis procedures will be discussed.
References
[Ab08] D.Abriola and A.A.Sonzogni, Nuclear Data Sheets 109 (2008) 2501.
[Ca25] S.Cannarozzo et al., Physics Letters B871 (2025) 1.
[Ch20] J.Chen and B.Singh, Nuclear Data Sheets 164 (2020) 1.
[El13] S.Eliseev et al., Applied Physics B: Lasers and Optics 114 (2013) 396.
[Ha07] U.Hager et al., Nuclear Physics A793 (2007) 20.
[Hi91] John C. Hill et al., Physical Review C43 (1991) 2591.
[Sh83] K.Shizuma et al., Physical Review C27 (1983) 2869.
[Si21] B.Singh and J.Chen, Nuclear Data Sheets 172 (2021) 1.