Nustar Seminar

Size: px

Start display at page:

Download "Nustar Seminar"

Kristopher Reeves
5 years ago
Views:

Fritz Peter Heßberger GSI Helmholtzzentrum für f r Schwerionenforschung mbh, D-64291 Darmstadt,

1 Fritz Peter Heßberger GSI Helmholtzzentrum für f r Schwerionenforschung mbh, D Darmstadt, Germany Helmholtz Institut Mainz, D-5599 D Mainz, Germany Nustar Seminar Version:

2 First Prediction of Superheavy Elements A. Sobiczewski, F. Gareev, B.N. Kalinkin, Phys. Lett. 22, 5 (1966) Calculations of energies of proton and neutron levels for heavy nuclei A > 2 show gaps for Z = 82 (known) and Z = 114, as well as for N = 126 (known) and N = 184 (and also N = 228); gaps in the sequence of single particle levels can be interpreted as signature for shell closures

3 Predictions of Superheavy Elements (164) (164) Proton number Proton number Macroscopic Microscopic Calculations E gs < 1 MeV 1-2 MeV 2-3 MeV 3-4 MeV 4-5 MeV 5-6 MeV 6-7 MeV >7 MeV Z=114 Z=18 < Z= Z= >.25 N =152 N=152 N =162 N=162 N =184 N= H. Meldner Arkiv fys. 36,593 (1967) Neutron number R.Smolanczuk, A. Sobiczewski Proc. EPS Conf. Low Energy Nucl. Dyn., St. Petersburg, Russia, 1995 & priv. comm. konferenzen/tour_912/sobi

Predictions of Superheavy Elements Self-consistent Hartree-Fock-Bogoliubov (HFB) calculation using forces of Skyrme- or Gogny type and Relativistic Mean Field (RMF) calculations, using different

4 Predictions of Superheavy Elements Self-consistent Hartree-Fock-Bogoliubov (HFB) calculation using forces of Skyrme- or Gogny type and Relativistic Mean Field (RMF) calculations, using different parametrizations. SHF: SkP, SkI3, SLy6, SkI4; Gogny: D1S and RMF: NL3, NL-Z2. Results different for different parametrizations, also different from macroscopic-microscopic calculations: SkP predicts proton shell Z=126, other SHF param. rather Z=12, SkI4 shows also stromg shell effects at Z=114; SHF predict neutron shell essentially at N=184, partly strong shell effects also at N=172 RMF predict proton shell at Z=12 and strong neutron shell rather at N=172. From: M.Bender et al. Phys. Lett. B 515, 42 (21)

5 Predictions of Superheavy Elements Are superheavy nuclei different? Yes! Competition between short-range nuclear forces and long-range electrostatic repulsion results in the Coulomb frustration effects Electromagnetic interaction is highly non pertubative - gives rise to huge self-consistent polarization effects / rearrangement Is the concept of magicity useful in superheavy nuclei? Probably not! Because of very high level density and the Coulomb frustration effects (from: W. Nazarewicz, Contribution to FUSHE 212) Shell structure and Coulomb frustration E [MeV] j 13/2 4s 1/2 3d 5/2 3d 3/2 2g 7/2 1j 15/2 2g 9/ s 1/ E [MeV] j 13/2 3d 3/2 3d 5/2 2g 7/2 1j 15/2 2g 9/2 172 SLy6 E [MeV] j 13/2 4s 1/2 3d 3/2 3d 5/2 2g 7/ j 15/2 2g 9/2 RMF + BCS +QVC -12 From: E.Litvinova Contr. to FUSHE E [MeV] j 13/2 4s 1/2 3d 3/2 3d 5/2 2g 7/2 1j 15/2 2g 9/2 184

6 Physics Motivation for Nuclear Structure Investigations in the Region of SHE Why Nuclear structure investigations? Atomic nucleus is quantum mechanical ensemble of nucleons (p, n) Understanding nuclear structure of SHE is Properties determined by fundamental interactions - nucleon nucleon interaction - Coulomb interaction - spin orbit interaction -. essential for understanding their properties and stability Understanding nuclear structure Understanding fundamental interactions Superheavy nuclei (SHE) ensembles of extremely i.e. the large limits numbersof protons our world and neutrons despite of high density of nuclear levels gaps between single particle states occur at certain numbers of Z and N indicating shell closures no macroscopic ( collective ) fission barrier any more, stability against prompt disruption due to shell effects ; B f depends on single particle levels shell structure determines nuclear mass excess determines Q-values for α- and β- decay

7 Probing Shell crossing by α - decay Q α values reflect differences in masses and are thus extremely sensitive to changes in shell effects strong changes of Q α values when crossing shell; effect strongest when crossing p-shell at n-shell; effect diminishs at departing from n-shell At N = 172,17 no significant effect of p-shell Z=114 on Q α values expected Q / MeV chain going through N = 158 at Z = Z N s -4 (Q (Z) - Q (Z-2)) / MeV 1,,8,6,4,2, N s Z Q / MeV chains going at Z = 82 through N = 126 (shell) N = 12 N = Z (Q (Z) - Q (Z-2)) / MeV Z Q / MeV chains going at Z=114 through N = 184 (shell) 6 N = 172 N = (Q (Z) - Q (Z-2)) / MeV Z Z

8 Alpha - decay energies of SHE Q / MeV Z=112 Z=114 Z=12 Z=118 Z=11 Z=116 Z=18 Z=16 Z=14 Δ(Q α (exp) - Q α (theo)) mean = -.32 MeV at Z= symbols: exp. values lines calc. Sobiczewski & Smolanczuk neutron number graph/vortrag/qalfshe

9 E α - and T 1/2- values expected for Z = 12 isotopes E / MeV ,1,1 1E-3 1E-4 1E-5 1E-6 1E-7 1E-8 Myers, Swiatecki et al. Smolanczuk, Sobiczewski Typel, Brown, HFB-SKX Cwiok et al., HFB-SLy4 Litvinova, RMF Litvinova, RMF+VC 248 Cm( 54 Cr,4n) : E 1 α (expected) = MeV T α = 5.1 μs 249 Cf( 5 Ti,3n) : E 1 α (expected) = MeV T α = 1.5 μs 249 Cf( 5 Ti,4n) : E α (expected) = MeV T α = 1.3 μs T /s Separation times SHIP: ca. 2.1 s TASCA: ca..7 s Neutron number

10 Shape of α spectra of superheavy nuclei O Even even nuclei have quite simple α-spectra; one main transition gs gs O weak transitions into gs rotational band are only visuble as shoulders as E2 transitions within band are converted O at low statistics considerable straggling of α-particle energies must be considered even for a single transition 48 Ca + 28 Pb, E = 4.55 MeV/u counts Lr(1) 253 Lr(2) 54 Cr + 29 Bi --> 261 Bh + 2n 257 Db(2) 257 Db(2) 257 Db(1) 261 Bh E / kev 25 A Z (ee) 254 No 2 <1% 15-2% 8-85% 25 Fm Counts A-4 Z-2 FWHM = 22 kev Cf 254 Fm E / kev

11 Alpha decay of of 27 Ds 27 Ds Scattering of α-energies of 27 Ds within MeV; Energies > 11 MeV attributed to α-decay of K isomer; energies < 11 MeV to α decayof gs But: fine structure in gs decay indicated gs K - isomer counts counts counts Ds, t(er- ) > 1 ms 1,5 11, 11,5 12, 12, E / MeV 27 Ds, t(er- ) < 1 ms Fit: FWHM = 4 kev 1,9 11, 11,1 11,2 11, E / MeV 266 Hs Fit: FWHM = 4 kev 2 D.Ackermann, GSI-Scientific Reports 21 & 211 and to be published 1,1 1,2 1,3 1,4 1,5 E / MeV

12 Production at GSI Alpha decay of 288 Fl (Z=114) of decay spectrum of 288 Fl (Z=114) TASCA: 244 Pu( 48 Ca,4n) 288 Fl 11 decays (8 fully stopped in FPD) detector res. 25 kev (FWHM) (J.M. Gates et al. PRC 83, (211)) SHIP: 248 Cm( 48 Ca,4n) 292 Lv α 288 Fl 4 decays (2 fully stopped in FPD) detector res. 24 kev (FWHM) (S. Hofmann et al. EPJ A 48:62 (212)) Alpha spectrum cannot be described by a single transition line half-lives are in agreement within error bars Fine structure in the alpha decay?? (not expected) Isomer decaying by alpha emission??? (not expected) calibration effect?? (two independent experiments) counts counts TASCA - Data, J.M. Gates et al. PRC 83, (211) SHIP - Data, S. Hofmann et al. EPJA (212), 48:62 SHIP + TASCA - Data, BINS = 1 kev, Gaussians: FWHM = 4 kev / -.1 s / -.16 s E / kev

13 Playground for Nuclear Structure Investigations in Transfermium Region Proton number Proton number 1 < < < < < < <.5.5 < <.1.1 < < < < discovered < <.2 at SHIP -.2 < < -.5 < < -.2 =< < Fm < <.25 new or improved decay >.25 data measured at SHIP 18 - or X-rays measured new isomeric states discovered 241 Fm 251 Lr 25 No Lr 25 No Nuclear Structure investigations 252 Lr 253 Lr 254 Lr 255 Lr 256 Lr 257 Lr 258 Lr 259 Lr 26 Lr 261 Lr 262 Lr require a large number (>>1) of 251 No events; 252 No 253 No 254 No presently 255 No 256 No 257 No 258 No can 259 No 26 No be 262 No reached in reasonable 256 Md irradiation 257 Md 258 Md 259 Md 26 Md times up to 152 Z = 11, 162where cross-18sections 82 are in the range 2 μb (254No) 152 to 15 pb (27Ds) P.Möller et al. At. Data and Nucl. Data Tab. 59, 185 (1995) Neutron Number 26 Bh 258 Sg 259 Sg 269 Ds 27 Ds 271 Ds 266 Mt 268 Mt 27 Mt 263 Hs 264 Hs 265 Hs 266 Hs 267 Hs 268 Hs 269 Hs 27 Hs 261 Bh 262 Bh 264 Bh Bh 266 Bh 267 Bh 26 Sg 261 Sg 262 Sg 263 Sg 264 Sg 265 SgBh Sg Bh 255 Db 256 Db 257 Db 258 Db 259 Db 26 Db 261 Db 262 Db 263 Db 267 Db 253 Rf 254 Rf 255 Rf 256 Rf 257 Rf 258 Rf 259 Rf 26 Rf 261 Rf 262 Rf 263 Rf 252 Lr 253 Lr 254 Lr 255 Lr 256 Lr 257 Lr 251 No 252 No 253 No 254 No 255 No 256 No 257 No 258 No 259 No 26 No 262 No 245 Md 246 Md 247 Md 248 Md 249 Md 25 Md 251 Md 252 Md 253 Md 254 Md 255 Md 256 Md 257 Md 258 Md 259 Md 26 Md 243 Fm 244 Fm 245 Fm 246 Fm 247 Fm 248 Fm 249 Fm 25 Fm 251 Fm 252 Fm 253 Fm 254 Fm 255 Fm 256 Fm 257 Fm 258 Fm 259 Fm Bh 258 Sg 259 Sg Neutron number 269 Ds 27 Ds 271 Ds 266 Mt 268 Mt 27 Mt 263 Hs 264 Hs 265 Hs 266 Hs 267 Hs 268 Hs 269 Hs 27 Hs Lr 259 Lr 26 Lr 261 Lr 262 Lr Sg 261 Sg 262 Sg 263 Sg Bh 265 Bh 266 Bh 267 Bh 255 Db 256 Db 257 Db 258 Db 259 Db 26 Db 261 Db 262 Db 263 Db 253 Rf 254 Rf 255 Rf 256 Rf 257 Rf 258 Rf 259 Rf 26 Rf 261 Rf 262 Rf 263 Rf 245 Md 246 Md 247 Md 248 Md 249 Md 25 Md 251 Md 252 Md 253 Md 254 Md 255 Md 243 Fm 244 Fm 245 Fm 246 Fm 247 Fm 248 Fm 249 Fm 25 Fm 251 Fm 252 Fm 253 Fm 254 Fm 255 Fm 256 Fm 257 Fm 258 Fm 259 Fm 264 Sg 265 Sg 266 Sg 267 Sg Db 162

14 Velocity separator SHIP SHIP Separation time: 1 2 μs Transmission: 2 5 % Background: 1 5 Hz Det. E. resolution: kev Det. Pos. resolution: 15 μm Dead time: 25 μs

15 Schematic Experimental Set-up for SHE Decay measurments Target Separator Focal Plane Detectors Beam ER Beam Detectors, CE (in beam spectroscopy) TOF (anti-coincidence) 'Backward' 'Stop' - ray, CE (segmented) sf sf

16 Experimental Set-up Detector system T 1 TOF T 2 'Backward - Detector' Basic principle: a) Nuclei are stopped in a silicon detector (pos. sens., strip-detector, pixel detector), in which α-particles, CE, fission fragments are measured b) Ge-detector for γ-measurements (Clover, planar Ge-detectors) c) Backward ( Box ) detecors for measuring particles escaping the stop detector ( E + E R ) 'Stop-Detector' CE (E CE ) VETO ' -Clover -Det.') (E + E CE ) (E ) t flight = (T 2 -T 1 ) ER ER (E ) 'light particle (lp)' (,p) E lp E lp anticoincidence 'Backward - Detector' d) TOF detectors for mass discrimination of incoming particles (together with E-measurement in stop detector) and anticoincidence (discrimination of incoming particles from decays in the stop detector) e) (optional: VETO detectors for discrimination of decays and light particles (p,α..) from target area

17 Ereignisse Energy summing α-particles and CE IC K (Fm) IC IC 249 Fm (84) 9/2-[624] 11/2+ 9/2+ 7/2+[624] No F.P. Heßberger et al. EPJ A 29, (26) Implant. counts Fm 255 No 256 No E / kev F.P.Heßberger E / kev coinc (x.33) coinc (x.17) coinc M. Asai et al. PRC 83, (211) He-Jet counts E / kev F.P.Heßberger

18 Features of Nuclear Structure Investigations Single particle levels - systematic trends in odd-mass Es isotopes - relation to nuclear deformation - relation to supposed proton shell Z = 114 Quasiparticle states in even even N = 152 isotones - systematics of K isomers Nuclear structure and fission properties - spin dependence of the fission barrier - relation between spin/parity and fission hindrance in odd mass nuclei (?) Ground state properties - nuclear structure investigation and ground-state mass determination

19 Systematics of Nilsson-Levels in Es - Nuclei Studied by α-γ Coincidence Measurements of Md-Isotopes Counts Ar + 29 Bi, E = 4.66 AMeV γ-rays in coincidence with -decays of 247 Md counts E / kev Counts Ca + 27 Pb, E = ( ) AMeV -rays coinc. E + E = ( ) MeV coinc. 'escape' -particles from 253 No ( = 9 nb) 222 kev 28 kev 253 Md ( eff = 2 nb) 34 kev 353 kev E / kev E / kev konferenzen/tan97/md253alga F.P.Heßberger

20 Decay schemes of odd-mass Md-isotopes (simplified) 247 Md 7/2 - [514] 249 Md 7/2 [514] 251 Md 7/2 [514] 253 Md 7/2 [514] 255 Md /2 [514] HF~1 826 HF~1 754 HF~3 71 HF~ / /2 [514] (E1) 7/2 [514] (E1) - 7/2 [514] (E1) - 7/2 [514] (E1?) - 7/2 [514] (E1) 45.2 (E1) 9/2+ 9/2 + 9/ /2 9/2 7/2 + [633] 7/2 + [633] 7/2 + [633] + 7/2 + [633] 7/2 [633] 243 (3/2- [521]?) (3/2- [521]?) Es (3/2 [521]?) 3/2 [521] Es 245 Es Es 251 Es graph/demo/nivmend F.P.Heßberger

21 Nilsson levels in odd-mass Es isotopes Nilsson single proton levels 5,3 45 theory: P.Möller et al. ADND59, 185 (1995), , ,225 f 5/ /2-[514] E / kev 2 7 E((7/2-[514])-(7/2+[633])),2 f 7/2 i 13/2 1 1/2-[521] 6 4,75 h 9/2 96 3/2-[521] 7/2+[633] 5, E((9/2+)-(7/2+)), Mass Number, Mass Number StrukturSWK/Abbildungen/Es_Isotope_deformation

22 Nilsson states in odd-mass Es - isotopes StrukturSWK/Abbildungen/Niv_Md_Vergleich_neu, experiment (f 5/2 ) E* / kev x1 +x1 243 Es 253+x2 +x2 245 Es 294+x3 +x3 247 Es 249 Es 1/2-[521] 251 Es 7/2-[514] 3/2-[521] 7/2+[633] 253 Es (h 9/2 ) (f 7/2 ) (i 13/2 ) E* / kev 6 4 3/2-[521] 7/2-[514] HFB - SLy4 (Chatillon et al. EPJ A3, 397 (26)) E* / kev 6 4 1/2-[521] cranked shell model (Zhang et al. PRC85,14324 (212)) 2 7/2+[633] 1/2-[521] 2 7/2-[514] 3/2-[521] 7/2+[633] 243 Es 245 Es 247 Es 249 Es 251 Es 253 Es 245 Es 247 Es 249 Es 251 Es 253 Es macros.-micros. (Parkhomenko & Sobiczewski, Act. Phys. pol. B35,2447 (24)) 6 7/2-[514] 6 macros. - micros (+TCSM) Adamian et al. PRC82,5434 (21) E* / kev 4 1/2-[521] E* / kev 4 9/2+[624] 7/2-[514] 5/2-[523] 2 3/2-[521] 2 7/2+[633] 243 Es 245 Es 247 Es 249 Es 251 Es 253 Es 255 Es 3/2-[521] 7/2+[633] 243 Es 245 Es 247 Es 249 Es 251 Es 253 Es 255 Es

23 Systematics of Nilsson levels in N=149 isotones 27 Pb( 48 Ca,2n) 253 No : σ 18 nb ; 33 α-decays collected in 96 h irrad. time counts 12k 11k 1k 9k 8k 7k 6k 5k 4k 3k 2k 1k K-x-rays (Fm) 151 kev 222 kev 28 kev counts kev 58 kev 128 kev 29 kev E / kev 297 kev 67 kev E / kev hess/konferenzen/tan_97/no253_r239_r26 F.P.Heßberger,

24 Decay Properties of N=151 Isotones Z = 1 Z = 12 Z = 14 9/2 - [734] 251 Fm 9/2 - [734] 253 No 9/2 - [734] 255 Rf 8 7/2 - [743] (6639,.6) (6834,.87) 7/2 - [743] (6929,.18) (762,.1) E * / kev 6 4 9/2 - [734] 7/2 + 5/2 + [622] (84,.96) (878,.4) (873, >.9) E1 (.24) E1 (.57) E1 (.19) 9/2 - [734] 2 11/2 + M1 5/2 + [622] 11/2 + E1 (.23) E1 (.63) 9/2 + 9/2 + 9/2 + 7/2 + [624] 7/2 + [624] 7/2 + [624] 247 Cf E1 (.14) 249 Fm M1 9/2 - [734] E1 (.45) E1 (.55) 251 No I. Ahmad et al. PR C 8, 737 (1973) F.P. Heßberger EPJ D 45, 33 (27) F.P.Heßberger et al. EPJ A 3, 561 (26)

25 Systematics of low lying Nilsson-levels levels in N=149 isotones Theory (A.Parkhomenko, A.Sobiczewski, Act. Phy. Pol. B 36, 3115 (25)) 6 7/2 - [743] Experiment 1/2 + [631] 5 7/2 - [743] 5 E * / kev 4 3 E * / kev 4 3 9/2 - [734] 1/2 + [631] 5/2 + [622] /2 + [622] 9/2 - [734] s 7/2 + [624] 243 Pu 245 Cm 247 Cf 249 Fm 251 No 253 Rf 255 Sg 7/2 + [624] 243 Pu 245 Pu 247 Cf 249 Fm 251 No

26 Counts Decay of a K-Isomeric state in 26 Pb( 48 Ca,2n) 252m No 17 (4+ --> 2+) (line dublett) K (+ 123?) (6+ --> 4+) 224 (8+ --> 6+) No in No 252 No (25) 1229 (7-) (6-) 173 (5-) (4-) 966 (3-) 929 (2-) 1 ms 1254 kev (8 _ ) 5 No252iso F.P.Heßberger E / kev No252_KIsomer_1486 F.P.Heßberger ,5-,8-9/2+ 7/2-1/2-7/2+ 3/2-1/ /2+ 1/2+ 7/2+ 11/2-9/2-7/2+ 5/2+ Z N B. Sulignano et al. EPJ A 33, 327 (27) 8-

27 K-isomers in N=15 isotones E* / kev quasi p 2-quasi n calc. J.-P. Delaroche et al. Nucl. Phys. A 771, 13 (26) 8+ (7/2-,9/2-) 4+ (1/2+,7/2+) 7- (5/2+,9/2-) 4- (3/2-,5/2+) exp. 8- T 1/2 =? 8- (7/2+,9/2-) 246 Cm 3- (1/2-,5/2+) 6+ (5/2+,7/2+) 5- (3/2-,7/2+) 2+ (1/2-,3/2-) 248 Cf 4+ (1/2-,7/2-) 7- (7/2+,7/2-) 1.8 s 4- (1/2-,7/2+) 25 Fm 4+ (1/2-,7/2-).1 s 252 No Decay schemes of 252 No and 25 Fm similar; but different to that of 254 No!! Suggests similar structure of isomers in 252 No and 25 Fm. Supported by calculations; lowest 2quasi particle configuration predicted as 2quasi neutron state with I π = 8 -. Common trend in N=15 isotones? next heavier candidate is 254 Rf (T 1/2 = 23 μs (sf)); If 2quasi neutron state K isomer should be expected!

28 K isomer in odd-mass nucleus 251 No counts counts (92.2) K (No) K (No) E / kev F.P.Heßberger et al. EPJ A 3, 561 (26) Pb( 48 Ca,3n) 251 No γ s coincident ER Pb( 5 Ti,2n) 255 Rf γ s coinc. -decay 255 Rf tentative decay scheme E * / kev /2 + [613]? 9/2 - [734] 1/2 + [631] 9/2 + 7/2 + [624] ca. 2 s, > s.8 s? (782) (714) ~ 23.6 E1 251 No 9/2 - [734] (E1) Rf

29 EC decay study of of 253 No -- Energy levels in 253 No Production: 253 No EC ( 5%) 253 Md EC ( 99%) 253 Fm 76.1 K (Fm) coinc. K -X-rays (Fm) counts/kev K (Md) K (Md) 15 ( 253 Fm) 188 ( 253 Fm) in 253 Fm 253 Fm Coinc. K -X-rays of Md 394 ( 253 Md) 451 ( 253 Md) 12 coinc. E =15.2 kev E / kev counts coinc. E =187.5 kev Counts CE coinc. K X-ray - - coincidences (E = 15.2, kev) E CE (mean) = 19 kev CE coinc. K X-ray - K X-ray coincidences E / kev E CE / kev

30 EC decay study of of 253 No -- Energy levels in 253 No in 253 Fm 253 Fm 11/2-[725] isomeric state identified; decay pattern established on the basis of systemtics ( 251 Cf) No connections to low energy level studied by Asai et al. via -decay of 257 No established CE energy suggests 7/2+[613] at 14 kev strong X-ray X-ray coincidences suggest also EC-decay in a so far not identified level E / kev counts 16 8 T 1/2 =.56 ±.6 s t( (188 kev) - CE) / rel. units Fm253_TAC_E t(ce - gamma) / rel. units Md 7/2-[514]?.5±.3 s Fm S. Antalic et al. EPJA 47:62 (211)? x+398 9/2+[615] x /2-[725] x /2+ x+61 x ~ /2+[613] / /2+[622] /2+ 5/2+ 3/2+ 1/2+[62]

Nuclear Structure and spontaneous fission Due to angular momentum conservation fission of nuclei with odd Z, odd N Cannot follow the most energetic favourable path effective enhancement of fission

31 Nuclear Structure and spontaneous fission Due to angular momentum conservation fission of nuclei with odd Z, odd N Cannot follow the most energetic favourable path effective enhancement of fission barrier ( specalisation energy ) enhancement of fission life-times hindrance of fission for nuclei with odd numbers of n and/or p J. Randrup et al. NPA 217, 221 (1973) Spin, Parity established; T sf of neighboring ee nuclei known Spin, Parity uncertain and/or T sf of neighboring ee nuclei from theory (End-)members of chains from hot fusion HF D. Vretenar Priv. comm. (212) /StrukturSWK/Abbildungen/sf_BHF; F.P.Heßberger Z 2 / A

32 Nuclear Structure Effects on Hindrance Factors No evidence for relation between HF and spin/parity of fissioning level In spin-up states ( ) HF of more fissile nuclei tends to be lower, while in spin-down states ( ) HF of more fissile nuclei tends to be higher accidential or nuclear structure effect?? Rf, 1/2 + [62] 259 Sg, 1/2 + [62] 239 Pu, 1/2 + [631] 261 Rf, 3/2 + [622] 261 Sg, 3/2 + [622] 241 Pu, 5/2 + [622] 243 Cm, 5/2 + [622] 255 Fm, 7/2 + [613] 235 U, 7/2 - [743] 245 Cm, 7/2 + [624] 251 No, 7/2 + [624] 249 Cf, 9/2 - [734] 255 Rf, 9/2 - [734] 257 Fm, 9/2 + [615] 243 Am, 5/2 + [523] 241 Am, 5/2 + [523] 249 Bk, 7/2 + [633] 253 Es, 7/2 + [633] Hindrance Factor /StrukturSWK/Abbildungen/sf_BHF; F.P.Heßberger

SHIPTRAP 9 Mean time of flight / s 85 8 75 253 No 2+ 7-3 -2-1 1

detection fusion products from SHIP Buncher 3 Purification Trap

33 SHIPTRAP 9 Mean time of flight / s No Excitation frequency / Hz Stopping Cell 1 2 Extraction RFQ 1. deceleration 2. cooling 3. accumulation 4. purifucation 5. storage 6. detection fusion products from SHIP Buncher 3 Purification Trap 4 Measurement Trap 6 5 Detector Downstream Experiments Masses Measured 252,253,254,255 No 255,256 Lr

34 Masses of odd-a N-Z Z = 51 Nuclei Symbiosis of Mass Measurements and Spectroscopy 245 Cf 249 Fm 253 No ca Rf Sg /2+[624] 1/2+[631] 265 Hs ca /2-[734] 7/2+[624] 269 Ds 143 5/2+[622] 9/2-[734] /2+[622] 1/2+[62] 7/2+ 3/2+[622] (1/2+[62]?) tentative (1/2+[62]?) (7/2+[613]?) (9/2+[615]?) tentative strukturswk/abb_wmf/reserve/niveausnz51 F.P.Heßberger counts ( m exp - m AME3 )c 2 / MeV) Ds - rays coincident 225 with 4 -decays of 253 No Hs Sg Rf E / kev No Fm Cf E / kev 75, ( m exp - m theo )c 2 mc 2 / MeV F.P. Heßberger et al. EPJ A 48:75 (212) 7/2 - [743] / MeV) 9/2 - [734],2, -,2 5/2 + [622] 11/2 + 2, 1, ,,5, 9/2 + 7/2 + [624] (E1,.27) (HF = 48) E / kev Möller et al Liran et al (E1,.61) (E2) 29.3 (M1) (M1) 9/2 - [734] (762,.25) 249 Fm (84,.96, HF = 3.1) 15.4 (E1,.12) 253 No (875,.42, HF = 139) Atomic number Decay scheme: F.P. Heßberger et al. EPJ A 48:75 (212)

New Detector Set-up - TASISpec Configuration of TASISpec (TASCA in Small Image Mode Spectroscopy) Double sided Si-strip detector (DSSSD); implantation detector, 32x32 strips, active area 58 mm x 58

35 New Detector Set-up - TASISpec Configuration of TASISpec (TASCA in Small Image Mode Spectroscopy) Double sided Si-strip detector (DSSSD); implantation detector, 32x32 strips, active area 58 mm x 58 mm;.31 mm thickn. Box of 4 single sided strip detectors (SSSSD) 6 mm x 6 mm active aream 1. mm thickn. 1 seven-crystal Ge - Cluster detector (behind implantation detector) 4 four-crystal Ge-Clover detectors expected γ-efficiency 4 % at 2 kev L.L. Andersson, D. Rudoph et al., NIM A 622, 164 (21)

TRAP assisted spectroscopy First Commissioning Experiment in September 29: 17 Er( 48 Ca,5n) 213 Ra Main features: Clean samples, mass separated (no

36 TRAP assisted spectroscopy First Commissioning Experiment in September 29: 17 Er( 48 Ca,5n) 213 Ra Main features: Clean samples, mass separated (no admixtures with isotones) Avoid energy summing of α-particles with conversion electrones D. Rudolph et al. GSI Annual Report 29, NUSTAR-SHE-8, 177 (21)

37 Next steps?? Limited beamtime available 213 / 214 2x4 weeks for experiments Experiments should be GSI unique -> 5 Ti beam Nuclear structure investigations of Rf- and Db isotopes 5 Ti Pb, 29 Bi; σ (2 (2-15) nb; requires 5-1 days of beamtime / experiment

38 Exists a K-Isomer in 254 Rf? in T 1/2 = 23 ±3 s 26 Pb( 5 Ti,2n) 254 Rf K isomer, T 1/2 = x ms 5 counts Deadtime of DAQ T 1/2 = 9 +9/-3 ms Or is K-isomer unstable against fission with τ < 23 μs?? 28 T 1/2 = /-.3 s Pb( 5 Ti,2n) 256 Rf? (contamination) 26 Pb( 5 Ti,n) 255 Rf 1E-3,1, t(er-sf) / ms gs, T 1/2 = 23 s ms sf-activity probably 256 Rf from 28 Pb target contamination Intensity would 26 be very low: i(k-isomer)/i(gs) <.25 Pb( 5 Ti,2n) 254 Rf Is lifetime of theσ 2.4 isomernb only some (tens) of μs or lower?? Is 23 μs activity 7 K-isomer sf/day lifetime 1pμA of gs much lower?? sf 23 s sf x ms New measurement at TASCA (April 212); Data are under evaluation (J. Khuyagbaatar) F.P.Heßberger et al. Z.Phys. A359, 415 (1997)

39 Decay Properties of N=151 Isotones Z = 1 Z = 12 Z = 14 E * / Ereignisse kev /2 - [743] 9/2 - [734] 7/2 + 5/2 + [622] 11/2 + 9/2 - [734] E1 (.24) E1 (.57) (6639,.6) E1 (.19) M1 251 Fm 27 Pb( 5 Ti,2n) 255 Rf σ 1 nb b α 5 % 1 1pμA (6834,.87) 7/2 - [743] (6929,.18) 9/2 - [734] 5/2 + [622] 11/2 + 9/2 - [734] E1 (.23) E1 (.63) (762,.1) E1 (.14) (84,.96) M1 253 No (878,.4) 9/2 - [734] 9/2 + 9/2 + 9/2 + 7/2 + [624] 7/2 + [624] 7/2 + [624] 247 Cf 86 K (No) Fm E1 (.45) 9/2 - [734] E1 (.55) 251 No (873, >.9) 255 Rf E / kev 24 StrukturSWK/Abbildungen/Rf255_alga_R218_R273 Stand: I. Ahmad et al. PR C 8, 737 (1973) F.P. Heßberger EPJ D 45, 33 (27) F.P.Heßberger et al. EPJ A 3, 561 (26)

40 Identification 11/2-[725] level in 11/2-[725] (1/2+) (9/2+) (3/2+) (5/2+, 7/2+) 5/2+[622] 11/2-9/2-11/2-9/2-[734] (E2) 91 (M1) 167 M2 (+E3) E * / kev α(8155 kev) / 1pμA No (8155, 4%) 19/2-17/2- (24±2 s) 2 15/2-13/ No (~55 s)? 255 (56 s) >15 ~15 s? (845) 7.51±.5.58±.6 (.99±.1) 28 Pb( 5 Ti,n) 257 Rf σ 1 8 nb i( 257m Rf) 6% 851 (1) 78 (M1) 9/2-[734] 11/2-[725] 1/2+[62] (M1) 257 Rf 615 (E2) (M1) 82 (M1) ±.5.58± (.99±.1) (1).65± ±.7 s 5.5±.4 s 15/ / /2-877 (11/2 - [725]) 21/2-19/ /2-3 γ(877 kev) / 1pμA /hess/strukurswk/abbildungen/no253m1testschema F.P.Heßberger, in 253 StrukturSWK/Abbildungen/Rf257_Zerfall_112 F.P.Heßberger, No 253 No

41 Decay of of 258 Db 258 Db (Running project: U278 (L.-L. Andersson et al.) 29 Bi( 5 Ti,n) 258 Db σ 4.3 nb α(7%), EC (3%) 7 α/day pμa s) α(9166) 254 Lr α 35 SF/day 258 Db 1pμA s) α(915) γ(221.5) 254 Lr 258 Db (3.6 s) EC 258 Rf sf 2 α-decaying levels in 258 Db and 254 Lr??? 258 Db (2. s) α(9196) 254 Lr α 258 Db (1.8 s) α(9196) 254 Lr EC 254 No α 258 Db (1.8 s) α(914,9134) γ(156.8) 254 Lr

7.5 AMeV cw LINAC for the GSI SHE Program Proposal submitted September 29 (W. Barth, GSI) (not yet funded) Cooperation: GSI Darmstadt, Helmholtz Institute Mainz, Inst. Applied Phys.

42 7.5 AMeV cw LINAC for the GSI SHE Program Proposal submitted September 29 (W. Barth, GSI) (not yet funded) Cooperation: GSI Darmstadt, Helmholtz Institute Mainz, Inst. Applied Phys. Goethe Universität Frankfurt Main Features: ( new 28 MHZ ECR source, in progress) ( new RFQ, in commissioning) energy range AMEV 1% duty cycle (presently 25%) intensity increase (> x1) improved beam quality Upgrade presently in progress 28 GHz ECR source + High Charge Injector (RFQ, IH)

The velocity filter SHIP (1976) 1976 212 Small entrance aperture of 2.7 msr since it was believed to produce SHE in symmetric reactions 2,6 2,4 2,2 2, 1,8 1,6 1,4 1,2 1,,8,6,4 22 Ne + 197 Au, 5.

43 The velocity filter SHIP (1976) Small entrance aperture of 2.7 msr since it was believed to produce SHE in symmetric reactions 2,6 2,4 2,2 2, 1,8 1,6 1,4 1,2 1,,8,6,4 22 Ne Au, 5.2 AMeV, R267, (mp /m t )=.112 ( 214 Ac) / SCC (relative) TP: normal, SHIP normal, Target: 324 g/cm 2 TP: normal, SHIP Popeko, Target: 324 g/cm 2 TP: normal, SHIP Popeko, Target: 324 g/cm 2 TP: normal, SHIP normal, Target: 396 g/cm 2 TP: normal, SHIP Popeko, Target: 396 g/cm 2 TP: +3 SHIP, SHIP normal, Target: 324 g/cm 2, D5=1.325 TP: +3 SHIP, SHIP normal, Target: 324 g/cm 2, D5=1.3 TP: +3 SHIP, SHIP Popeko, Target: 324 g/cm 2, D5=1.35 2,4 2,2 2, 1,8 1,6 1,4 1,2 Data from: F.P.Heßberger et al., Lecture Notes in Physics 317, 289 (1988) D. Ackermann, Diploma Thesis, 1988 Experiment (ER from 4 Ar Yb, E = 4.6 AMeV) 'Original' (1976) SHIP target position +17% +15% transmission / rel. units Monte Carlo Simulation present Targetposition (79.5 cm) 1,,2, hess/strukturswk/abb/ship/targetverschiebung distance from von 'original' - target position / cm Nr. Measurement StrukturSWK/Abb_WMF/EffSHIP_NeAuTV

44 New Separators Replacement of SHIP, in operation since 1976 (under consideration) Target ('high power' targets) (for i > 1 p A) (z p > 6.2 x 1 13 /s) A/q - Separator (A/q) / (A/q) = (3-4) to SHIPTRAP, Laser spectroscopy, MultiTOF primary beam Preseparator beam focussing intensity distribution clean energy (remove scattered particles) Wienfilter 2 - stage aperture >1 msr (variable) accpted charge width >±15 % accepted velocity width >±5 %? Detectorsystem ER,, CE, sf ( >4%) fast, t(ev n -ev n+1 )<.5 s digital electronics StrukturSWK/Abbildungen/SuperSHIP F.P. Heßberger, Proc. Int. Conf. Beyond 21, Cape Town, SA, Feb. 21, (World Scienfic), 675 (211)

45 Conclusions Nuclear structure investigations are the powerful tools to understand the properties of heaviest nuclei in terms of, e.g. nuclear forces Coulomb interaction in strong fields residual interactions like spin-orbit interaction ordering of nuclear levels identification of proton and neutron shells the nuclear fission process the stabilty of (multi) quasi-particle states mod. beam-times needed for nuclear structure investigations (2-15 d) Search for new elements requires >>1 d However, times of naivety are over; further investigations require more beamtime (detailed studies Z 16, studies at Z > 16) higher beam intensities ( cw Linac ) fast digital electronic (for small halflives) higher γ-efficiency (e.g. TASISPEC) new, efficient separators (high transmission, low charged particle background, low γ- and neutron background, mass selectivity )

46 SHIP SHE Spectroscopy Collaboration: GSI, Darmstadt D.Ackermann, M.Block, S.Heinz, F.P.H., S.Hofmann, B.Kindler, I.Kojouharov, J.Khuyagbaatar, B.Lommel, R.Mann, B.Sulignano, M. Dworschak (former members) Helmholtz Institut Mainz L.-L.Andersson, E. Minaya, M. Laatiaoui Comenius University Bratislava, Slovakia S. Antalic, Z.Kalininova, S.Saro, M.Venhart, B.Streicher (former members) Ernst-Moritz-Arndt Universität Greifswald, Germany C. Droese University Jyväskylä, Finland M.Leino, J.Uusitalo FLNR JINR Dubna, Russia A.G.Popeko, A.Yeremin JAEA Tokai, Japan K. Nishio University of Lund, Sweden D. Rudolph Theory Support: A. Sobiczewski (NCNR Warsaw, Poland) E. Litvinova (EMMI Darmstadt, Germany; MSU East Lansing, USA) D. Vretenar, Lu Bingnan (Univ. Zagreb, Croatia)

Nuclear Structure of Superheavy Nuclei Investigated at GSI

Nuclear Structure of Superheavy Nuclei Investigated at GSI Fritz Peter Heßberger GSI Helmholtzzentrum für Schwerionenforschung mbh, D-64291 Darmstadt, Germany Helmholtz Institut Mainz, D-5599 Mainz, Germany