Spin-alignment and g-factor measurement of the $I^{\pi}$ = 12+ isomer in 192Pb produced in the relativistic-energy fragmentation of a 238U beam

Abstract

Abstract. The feasibility of measuring g-factors using the TDPAD method applied to high-energy, heavy fragmentation products is explored. The 2623 keV I π = 12 + isomer in 192 Pb with τ = 1.57 μs has been produced using the fragmentation of a 1 A GeV 238 U beam. The results presented demonstrate for the first time that such heavy nuclei produced in a fragmentation reaction with a relativistic beam are sufficiently well spin-aligned. Moreover, the rather large value of the alignment, 28(10)% of the maximum possible, is preserved during the separation process allowing the determination of magnetic moments. The measured values of the lifetime, τ = 1.54(9) μs, and the g-factor, g = −0. 175(20), agree with the results of previous investigations using fusion-evaporation reactions.

Gamma-ray spectroscopy of fission fragments with state-of-the-art techniques

“…Moreover, the deduced g factor of the 7 − (T 1/2 = 5.9(8) μs) isomeric state of 126 Sn, located at 2219 keV, confirmed the ν(h −1 11/2 d −1 3/2 ) configuration proposed for the 7 − isomers in neutron-rich Sn isotopes [287]. With the same setup, additional g-factor investigations of high-spin isomers in Sn and Pb isotopes were also performed exploiting relativistic fragmentation reactions [288,289].…”

Large-scale shell-model calculations on the spectroscopy ofN<126Pb isotopes

“…There has been a long history measuring the quadrupole moments and magnetic moments of the isomeric 12 + , 13/2 + and 33/2 + states in Pb isotopes [35][36][37][38][39][40][41][42][43][44][45][46]. The I π = 12 + isomers in the even-even Pb isotopes have been interpreted as (vi 13/2 ) −2 quasi-particle states.…”

“…Moreover, there has been a long history studying the structure and electromagnetic properties of the spherical shell-model states in these Pb isotopes [34]. In particular, significant efforts have been made measuring the static quadrupole moments and magnetic moments (g factors) of the isomeric 12 + , 13/2 + and 33/2 + states in Pb isotopes [35][36][37][38][39][40][41][42][43][44][45][46], which are supposed to be spherical and are related to the coupling of neutrons in the orbital 0i 13/2 . Recent measurement on the quadrupole moments of the co-existing 11 − states are reported in Refs.…”

Large Longitudinal Spin Alignment of Excited Projectiles in Intermediate Energy Inelastic Scattering

“…These alignments can be so strong that particles emitted from the spinning fragments exhibit a forward-backward preference as they cast off ejectiles perpendicular to the spin direction, a fact that has been used for fragment-spin determination [10,12,15]. The cases for longitudinal alignment in reactions dominated by the strong interaction are usually limited to modest modifications of the spin projections from a uniform distribution [16,17]. Large longitudinal alignment has been seen in projectile fragmentation [18], though not at the level reported in this and a related work [19].…”