Nuclear Data Sheets for A = 171

Fast decay of a three-quasiparticle isomer inTm171

“…A γ-ray coincidence spectrum is shown in figure 2, illustrating transitions associated with isomeric decay from a level at 1674 keV. [7,8] and the present work is in agreement. However, two excited members of the 7/2 + band, above the 636 keV level, had been tentatively identified by Drissi et al [7], with γ-ray transitions at 108, 129…”

“…A previous study [7] of this nuclide with the same reaction had revealed rotational bands up to I = 19/2 built on the T 1/2 = 1.9 y, 1/2 + ground state and a 2.6 µs, 7/2 − state at 425 keV, each of one-quasiparticle character. A 1.3 ns, 7/2 + one-quasiparticle state at 636 keV is also well known [8]. The present work reports delayed feeding through the 7/2 + state, and establishes a three-quasiparticle, 19/2 + isomer with a half-life of 1.7 µs.…”

“…First, in 173 Lu the 7/2 + bandhead forms the ground state, whereas in 171 Tm the 7/2 + bandhead is an excited state. This was already known [8] to decay primarily by a 211 keV transition, which, in the present work, gives rise to different γ-γ-coincidence relationships. Second, and crucially, there are significant differences between the K-electron binding energies (59.4 keV for Tm, and 63.3 keV for Lu).…”

“…For the analysis of the electron conversion coefficients, the known [8] E1 character of the 308 keV transition (seen in figures 1 and 3) from the 2.6 µs, 7/2 − isomer in 171 Tm provides a convenient internal calibration, with a theoretical conversion coefficient of α K = 0.0151 [13].…”

“…The one-quasiparticle states (bandheads) shown in figure 1 have been assigned [7,8] the proton (π) However, it should be noted that this kind of calculation [15] has uncertainties ∼100 keV, so that the small (20 keV) difference between the experimental and calculated energies is fortuitous.…”