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Title: Novel Δ J = 1 Sequence in Ge 78 : Possible Evidence for Triaxiality

Here, a sequence of low-energy levels in 78 32Ge 46 has been identified with spins and parity of 2 +, 3 +, 4 +, 5 +, and 6 +. Decays within this band proceed strictly through ΔJ=1 transitions, unlike similar sequences in neighboring Ge and Se nuclei. Above the 2+ level, members of this sequence do not decay into the ground-state band. Moreover, the energy staggering of this sequence has the phase that would be expected for a γ-rigid structure. The energies and branching ratios of many of the levels are described well by shell-model calculations. However, the calculated reduced transition probabilities for the ΔJ=2 in-band transitions imply that they should have been observed, in contradiction with the experiment. Within the calculations of Davydov, Filippov, and Rostovsky for rigid-triaxial rotors with γ=30°, there are sequences of higher-spin levels connected by strong ΔJ=1 transitions which decay in the same manner as those observed experimentally, yet are calculated at too high an excitation energy.
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [1] ;  [5] ;  [6] ;  [7] ;  [8] ;  [7] ;  [7] ;  [7] ;  [7] ;  [9] ;  [10] ;  [9] ;  [7] ;  [5] ;  [7]
  1. Univ. of Maryland, College Park, MD (United States)
  2. Univ. of Maryland, College Park, MD (United States); Argonne National Lab. (ANL), Argonne, IL (United States); U.S. Army Research Lab., Adelphi, MD (United States)
  3. Argonne National Lab. (ANL), Argonne, IL (United States); Univ. of North Carolina, Chapel Hill, NC (United States)
  4. Argonne National Lab. (ANL), Argonne, IL (United States); United States Naval Academy, Annapolis, MD (United States)
  5. Univ. of Maryland, College Park, MD (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
  6. Argonne National Lab. (ANL), Argonne, IL (United States); TRIUMF, Vancouver, BC (Canada)
  7. Argonne National Lab. (ANL), Argonne, IL (United States)
  8. Argonne National Lab. (ANL), Argonne, IL (United States); Millsaps College, Jackson, MS (United States)
  9. Argonne National Lab. (ANL), Argonne, IL (United States); Univ. of Massachusetts, Lowell, MA (United States)
  10. Argonne National Lab. (ANL), Argonne, IL (United States); Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Report Number(s):
BNL-203652-2018-JAAM; BNL-203358-2018-JAAM
Journal ID: ISSN 0031-9007; PRLTAO
Grant/Contract Number:
SC0012704; AC02-06CH11357; AC02-98CH10886; FG02-94ER40834; FG02-97ER41041; FG02-97ER41033
Type:
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 120; Journal Issue: 21; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
OSTI Identifier:
1438428
Alternate Identifier(s):
OSTI ID: 1438290

Forney, A. M., Walters, W. B., Chiara, C. J., Janssens, R. V. F., Ayangeakaa, A. D., Sethi, J., Harker, J., Alcorta, M., Carpenter, M. P., Gurdal, G., Hoffman, C. R., Kay, B. P., Kondev, F. G., Lauritsen, T., Lister, C. J., McCutchan, Elizabeth A., Rogers, A. M., Seweryniak, D., Stefanescu, I., and Zhu, S.. Novel ΔJ=1 Sequence in Ge78: Possible Evidence for Triaxiality. United States: N. p., Web. doi:10.1103/PhysRevLett.120.212501.
Forney, A. M., Walters, W. B., Chiara, C. J., Janssens, R. V. F., Ayangeakaa, A. D., Sethi, J., Harker, J., Alcorta, M., Carpenter, M. P., Gurdal, G., Hoffman, C. R., Kay, B. P., Kondev, F. G., Lauritsen, T., Lister, C. J., McCutchan, Elizabeth A., Rogers, A. M., Seweryniak, D., Stefanescu, I., & Zhu, S.. Novel ΔJ=1 Sequence in Ge78: Possible Evidence for Triaxiality. United States. doi:10.1103/PhysRevLett.120.212501.
Forney, A. M., Walters, W. B., Chiara, C. J., Janssens, R. V. F., Ayangeakaa, A. D., Sethi, J., Harker, J., Alcorta, M., Carpenter, M. P., Gurdal, G., Hoffman, C. R., Kay, B. P., Kondev, F. G., Lauritsen, T., Lister, C. J., McCutchan, Elizabeth A., Rogers, A. M., Seweryniak, D., Stefanescu, I., and Zhu, S.. 2018. "Novel ΔJ=1 Sequence in Ge78: Possible Evidence for Triaxiality". United States. doi:10.1103/PhysRevLett.120.212501.
@article{osti_1438428,
title = {Novel ΔJ=1 Sequence in Ge78: Possible Evidence for Triaxiality},
author = {Forney, A. M. and Walters, W. B. and Chiara, C. J. and Janssens, R. V. F. and Ayangeakaa, A. D. and Sethi, J. and Harker, J. and Alcorta, M. and Carpenter, M. P. and Gurdal, G. and Hoffman, C. R. and Kay, B. P. and Kondev, F. G. and Lauritsen, T. and Lister, C. J. and McCutchan, Elizabeth A. and Rogers, A. M. and Seweryniak, D. and Stefanescu, I. and Zhu, S.},
abstractNote = {Here, a sequence of low-energy levels in 7832Ge46 has been identified with spins and parity of 2+, 3+, 4+, 5+, and 6+. Decays within this band proceed strictly through ΔJ=1 transitions, unlike similar sequences in neighboring Ge and Se nuclei. Above the 2+ level, members of this sequence do not decay into the ground-state band. Moreover, the energy staggering of this sequence has the phase that would be expected for a γ-rigid structure. The energies and branching ratios of many of the levels are described well by shell-model calculations. However, the calculated reduced transition probabilities for the ΔJ=2 in-band transitions imply that they should have been observed, in contradiction with the experiment. Within the calculations of Davydov, Filippov, and Rostovsky for rigid-triaxial rotors with γ=30°, there are sequences of higher-spin levels connected by strong ΔJ=1 transitions which decay in the same manner as those observed experimentally, yet are calculated at too high an excitation energy.},
doi = {10.1103/PhysRevLett.120.212501},
journal = {Physical Review Letters},
number = 21,
volume = 120,
place = {United States},
year = {2018},
month = {5}
}