Multiparticle configurations inN=84isotones located at the proton drip line

Abstract

Excited states in the proton-rich N = 84 isotones 156 72 Hf 84 , 157 73 Ta 84 , and 158 74 W 84 were observed using 102 Pd(58 Ni, xp2n) reactions at 270 MeV. γ rays were detected with the Gammasphere array of Comptonsuppressed Ge detectors coupled with the Argonne fragment mass analyzer and were assigned to individual reaction channels using the recoil-decay tagging method. Prompt γ-ray cascades were associated with the α decay of both the ground state and the 8 + isomeric state in 156 Hf, the h 11/2 state in 157 Ta, and the 8 + isomeric state in 158 W. The level schemes constructed for 156 Hf, 157 Ta, and 158 W are compared with these of lighter N = 84 isotones and are discussed within the framework of the shell model.

Fine structure in the α decay of high-spin isomers in Lu155 and Hf156

“…With eight protons and two neutrons above the core of 146 Gd, the high-spin isomer in 156 Hf has been interpreted to have a ν(f 7/2 h 9/2 )8 + configuration [26,27]. The isomeric state in 155 Lu, with an unpaired πh 11/2 proton, has been interpreted to have a π (h 11/2 ) 3 ν(f 7/2 h 9/2 )25/2 − configuration, which includes the addition of a proton seniority three structure [28].…”

“…The isomeric state in 155 Lu, with an unpaired πh 11/2 proton, has been interpreted to have a π (h 11/2 ) 3 ν(f 7/2 h 9/2 )25/2 − configuration, which includes the addition of a proton seniority three structure [28]. The existence of these isomers is explained by the 8 + (25/2 − ) state in 156 Hf ( 155 Lu) having been observed to have lower energy than that of the 6 + (23/2 − ) state of the ν(f 7/2 ) 2 [π (h 11/2 )ν(f 7/2 ) 2 ] band [27] ( [28]); hence forming a spin-trap isomer. The high-spin isomeric states will subsequently be referred to as 155 Lu(25/2 − ) and 156 Hf (8 + ) in this paper.…”

Excited states in the proton-unbound nuclideTa158

“…The transition marked with an asterisk (*) is an unresolved multiplet. (2) 149 ( (7) 58 (7) 782.2(10) 50(7) 439.2 (8) 42 (6) 1001.6(11) 984(51) E3 980(51) 583.9 (8) 75 (7) M1 77 (7) to specific configurations, given the uncertainties about their spin values we prefer not to speculate about their interpretation.…”

“…Current experimental techniques offer possibilities to investigate excited states in nuclei beyond the proton drip line, probing discrete states that are highly unbound to proton emission. Despite the low production cross sections for such neutron-deficient nuclei, extensive level schemes have been produced for proton-unbound nuclides, including many proton emitters [1][2][3][4][5][6][7][8][9][10][11][12][13]. In some cases the level schemes extend to excitation energies of several MeV.…”

Blurring the Boundaries: Decays of Multiparticle Isomers at the Proton Drip Line

“…The excitation energies, spins, and parities of yrast states that could be populated by proton emission from the new isomer in 158 Ta and the multiparticle isomers in 157 Ta and 153;154;155 Lu are known [16,[30][31][32][33]. Partial half-lives for proton-decay branches from the multiparticle isomers in 155 Lu and 157;158 Ta estimated by using a simple formula that reproduces measured proton-decay half-lives [34] are presented in Fig.…”