YRAST spectroscopy and g-factor measurements in 199Pb, 201Pb and 203Pb

Abstract

The half-lives and g-factors of high-spin states in 199,201,203pb were studied using 199,200,202Hg(α, 3n) reactions at E α =41 and 53 MeV. In-beam γ-ray spectroscopy including γγt-coincidence measurements were performed in order to interpret the level schemes. The measured half-lives are T 1 2 = 7.5 (3) ns, 10.0 (2) μ s and 55 (5) ns for the previously known 25 2 −, 29 2 − and 33 2 + states, respectively, in 199Pb and T 1 2 = 508 (5) ns and 63 (3) ns for the 29 2 − and the 25 2 − states, respectively, in 201Pb. A new isomer at 4559.2 + ° keV excitation energy with T 1 2 = 43 (3) ns and J π = 41 2 + is observed in 201Pb and a 33 2 − isomer at 2922.7 + Δ keV exitation energy with T 1 2 = 122 (4) ns in 203 Pb . The g-factors of the isomeric states were determined using the time differential perturbed angular distribution technique and the results are g( 29 2 −) = −0.0742 (2) and g( 29 2 −) = −0.0697 (4) for the 29 2 − states in 199Pb and 201Pb, respectively, indicating a predominantly three-neutron-hole configuration i −2 13 2 f −1 5 2 for these states. The g-factor of the 33 2 + state in 19 as g= −0.145(9) which agrees with a ν( i 13 2 −3 ) configuration. The g-factor of the 41 2 + sta g( 41 2 +) = −0.18 (4) indicates a five-quasiparticle configuration. The probable configuration for the 25 2 − isomer has also been suggested on the basis of the measured value of the g-factor g( 25 2 −) = −0.063 (3) in 201Pb and g( 25 2 −) = −0.059 (3) in 203Pb and the B(E2) values for t 25 2 −→ 21 2 − transitions in the odd Pb isotopes.