Spectroscopy of to Investigate its K-isomer Edward Parr
Motivation in Superheavies PROTONS Single Particle Energy (MeV) Single Particle Energy (MeV) NEUTRONS Next shell gaps predicted for Superheavy spherical nuclei 184 0 0.1 0.2 0.3 0.4 0.5 0.6 Quadrupole Deformation ( 2) Cross section to produce these nuclei is too low 114 0 0.1 0.2 0.3 0.4 0.5 0.6 Quadrupole Deformation ( 2)
Motivation in Superheavies PROTONS Single Particle Energy (MeV) Single Particle Energy (MeV) NEUTRONS 184 0 0.1 0.2 0.3 0.4 0.5 0.6 Quadrupole Deformation ( 2) Cross section to produce these nuclei is too low 114 0 0.1 0.2 0.3 0.4 0.5 0.6 Quadrupole Deformation ( 2)
Motivation in Superheavies PROTONS Single Particle Energy (MeV) Single Particle Energy (MeV) NEUTRONS Deformed shell gaps for transfermium nuclei 152 0 0.1 0.2 0.3 0.4 0.5 0.6 Quadrupole Deformation ( 2) 100 0 0.1 0.2 0.4 0.5 0.6 Quadrupole Deformation ( 2) Cross sections of nb b, production is experimentally viable 0.3
K-Isomers of nuclei J R nuclear symmetry axis Total spin of a nucleus I has rotational component R and single particle contribution J
K-Isomers of nuclei I nuclear symmetry axis k Total spin of a nucleus I has rotational component R and single particle contribution J I has projection k onto symmetry axis of nucleus
K-Isomers of nuclei I k k-isomer state I k decayed state A large change in k will inhibit the decay giving a relatively long lived K-isomer state
K-Isomer particle states Excitation Energy (kev) 1600 1400 8-8- 8-1200 3+ 1000 2-2- 800 254 600 250 Fm Theoretical results of energy levels in this region conflict
Excitation Energy (kev) K-Isomer particle states 1600 Proton excitation 1400 π[514]7/2- π[624]9/2+ Neutron excitation [734]9/2- [624]7/2+ [734]9/2- [624]7/2+ 1200 1000 800 254 600 250 Fm Theoretical results of energy levels in this region conflict Study K-isomer structures to infer single particle excitations into these levels
Experimental Setup Experiment took place at Jyväskylä in Finland Beam Energy = 218MeV JUROGAM target array RITU separator 48 Ca Beam GREAT focal plane array Fusion evaporation reaction; 206 48 Pb( Ca, 2n)
Recoil-Decay Tagging Counts Energy loss (kev) Raw JUROGAM Spectra Time of flight (10ns) Identifying recoils entering gas detector Energy (kev)
Recoil-tagged Spectra Counts Energy loss (kev) Recoil-Decay Tagging Energy (kev) Time of flight (10ns) Identifying recoils entering gas detector Gate on events in region of 2D histogram to identify
Identifying Decay Events 248 Fm 244 Cf 244 Cf 248 Fm Counts SF -s.f. 253 DSSSD-y Energy (MeV) Then select gated recoils which decay at focal plane with alpha energies or spontaneous fission
Ground State Rotational Band 485 328 374 416 453 Counts 167 277 224 Recoil tagged 485 453 416 374 328 277 224 167 Recoil-Decay tagged Energy (kev) events were identified and in-beam spectra taken at target position
Ground State Rotational Band 20+ 485 416 374 328 + tagged + (20+ 18+) 485 453 416 (14 12 ) (16+ 14+) (18+ 16+) 374 328 277 224 (8+ 6+) Recoil-Decay + + (10 8 ) (6+ 4+) (12+ 10+) 167 484.6(6) 18+ 453 Counts 167 277 224 Recoil tagged 16+ 14+ + 12 + 10 8+ Energy (kev) Harris model used to fit lower order transitions 453.3(4) 415.6(3) 373.8(5) 328.0(2) 277.6(2) 6+ 223.7(2) 4+ 167.2(2) 2+ 0+ 107.7(1) 46.5(1)
Recoil-Decay Tagged Isomeric Events Counts conversion electron spectrum DSSSD-x Energy (kev) Lower transitions are highly converted B. Sulignano, et al. Isomeric recoils decay at focal plane conversion electrons paired with RDT events to identify isomeric recoils
Half-life of - 8 K-Isomer Decays T1/2 = 111.3 (29) ms Time (ms) Time between recoil implantation and isomeric decay found Half life found consistent with previous: T1/2 = 110(10)ms
- 8 K-Isomer Rotational Band Counts 225 247 314 268 291 355 140 151 Pb Energy (kev) In-beam spectra of isomer events give prompt gamma at target position
- 8 K-Isomer Rotational Band 15- E2 (10-8-) (13-11-) (11-9-) 314 (gs transition) 247 (12-10-) 225 268 291 (15-13-) 355 355 Counts 13314 M1-151 291 11- - (11 10 ) 140 12-140 (12-11-) 151 10-268 9- Pb 247 8- Energy (kev) K-Isomer In-beam spectra of isomer events give prompt gamma at target position See rotational band built on K-isomer
Comparisons with Dynamic MOI vs angular frequency squared gs bands 2- bands 250 Fm Spin (ħ) Fm ℑ(2) (ħ2/mev) Energy (MeV) Energy vs Spin 250 250 Fm 8- band 8- band 2 (MeV2/ħ2) Comparing rotational band with similarly structured 250Fm
Comparisons with 8- bands Dynamic MOI vs angular frequency squared gs bands 2- bands 250 Fm Spin (ħ) Fm ℑ(2) (ħ2/mev) Energy (MeV) Energy vs Spin 250 250 Fm 8- band 8- band 2 (MeV2/ħ2) Comparing rotational band with similarly structured 250Fm
Configuration of K-Isomer Excitation Energy (kev) 1600 Proton excitation Neutron excitation? 1400 8-( [734]9/2- [624]7/2+) 1200 1000 800 254 600 250 Fm Use M1/E2 branching ratios to unambiguously assign a configuration to K-isomer
Collaborators P.T. Greenlees, M. Leino, U. Jakobsson, P. Jones, R. Julin, S. Juutinen, S. Ketelhut, H. Kettunen, M. Nyman, P. Rahkila, J. Saren, C. Scholey, J. Sorri and J. Uusitalo Department of Physics, University of Jyväskylä, Finland R.-D. Herzberg, P.A. Butler, J. Pakarinen, D. Rostron, P. Papadakis, E. Parr Department of Physics, University of Liverpool B. Sulignano, Ch. Theisen, A. Drouart, A. Görgen, W. Korten, J. Ljungvall, A. Obertelli and M. Zielińska DAPNIA/SPhN CEA-Saclay, France B. S. Hofmann, D. Ackermann, F.P. Heßberger, S. Heinz and J. Khuyagbataar GSI, Darmstadt, Germany S u M. Venhart, S. Antalic l Department of Nuclear Physics and Biophysics, Comenius University, Bratislava, Slovakia i g n a n o,