Saclay, 30 January 2007 Rauno Julin Department of Physics University of Jyväskylä FinlandJYFL In-beam Spectroscopy of In-beam Spectroscopy of Transfermium Nuclei Transfermium Nuclei
Outline: Introduction Even-Even 254 No ( Z =102, N = 152 ) 250 Fm ( Z =100, N = 150 ) Odd-Proton 251 Md (Z = 101, N = 150) 255 Lr (Z = 103, N = 152) Odd-Neutron 253 No (Z = 102, N = 151) Future plans
Spectroscopy of very neutron deficient and heavy nuclei at JYFL Can be produced via fusion evaporation with stable-ion beams and stable targets Can be produced via fusion evaporation with stable-ion beams and stable targets Short-living alpha or proton emitters → tagging methods Short-living alpha or proton emitters → tagging methods Cross-sections down to 1 nb Only levels near the yrast line populated
Recoil – Decay –Tagging (RDT) method
JUROGAM 43 Ge + BGO Eff. 4% RITU Gas-filled recoil separator Transmission % GREAT Focal plane spectrometer TDR Total Data Readout Triggerless data acquisition system with 10 ns time stamping + GRAIN the Analyser RDT Instrumentation at JYFL
prompt e - SACRED electron spectrometer at the RITU target
Transfermium Nuclei Produced in asymmetric cold-fusion reaction – X( 48 Ca,2n)Y → ideal for the gas-filled separator RITU → Only one reaction channel open → Total compound cross-section down to 50 mb → I beam up to 30pnA on a 0.5mg/cm 2 target in in-beam runs Fission dominates: : 1 → I beam limited by the Ge rate → Very low focal-plane rate → Enables long t 1/2 – α – tagging
254 No Z = 102, N = 152
254 No In-beam γ - rays from 208 Pb( 48 Ca,2n) 254 No - 2µb JUROGAM + RITU S. Eeckhaudt et al. EPJ A26, (2005), 227
In-beam γγ coincidences from 254 No 254 No ?
254 No-recoil gated in-beam conversion electrons from 208 Pb( 48 Ca,2n) 254 No Discrete lines + M1 continuum M1 P.A. Butler at al. PRL 89 (2002) SACRED + RITU data 254 No
254 No Levelscheme Long isomer Short isomer (16+) 55 s R.-D. Herzberg et al. Nature 442, (24 August 2006)
250 Fm Z = 100, N = 150
Singles Gamma-Ray Spectra from 204 Hg( 48 Ca,2n) 250 Fm (HgS targets) A. Pritchard, R.-D. Herzberg et al., University of Liverpool
250 Fm electron spectra
250 Fm preliminary PT Greenlees, RDH et al, preliminary! JUROGAM Tagged with isomer
250 Fm Levelscheme PT Greenlees, RDH et al, preliminary! ? ?
Kinematic moment of inertia J (1) even – even nuclei
Dynamic moment of inertia J (2) even – even nuclei
Dynamic moment of inertia even – even nuclei
250 Fm Dynamic Moment of Inertia J (2) Theory: M. Bender et al., NPA 723 (2003) 354 ♦ Exp
A Afanasiev, priv comm. 250 Fm Kinematic and Dynamic Moment of Inertia J (1) and J (2)
A. Afanasiev, PRC 67, 24309, (2002) Kinematic and Dynamic Moments of Inertia J (1) and J (2)
Odd - proton 251 Md 150, 255 Lr 152
[521]1/2 - [514]7/2- [633]7/2+
Electromagnetic Properties Odd-proton orbitals in 251 Md / 255 Lr B(M1)/B(E2) depends on (g K -g R )/Q 0 g K ~ 0.7 Mainly E2 [514] [633] g K ~ 1.3 Mainly M [521] a ~ 0.9 : g K ~ Mainly E2
Conversion coefficients Z ≈102
Prompt γ -ray spectroscopy of 251 Md and 255 Lr 205 Tl( 48 Ca,2n) 251 Md ~ 760 nb (A. Chatillon, Ch. Theisen et al. ) 209 Bi( 48 Ca,2n) 255 Lr ~ 300 nb (S. Ketelhut, P. Greenlees et al.)
Recoil Tagging γγ coincidences First rotational band in an odd-Z transfermium No signature partner : K=1/2 251 Md
Dynamical Moments of Inertia J (2) J (2) (hbar 2 MeV -1 ) Rotational Frequency
251 Md Dynamic Moment of Inertia J (2) Theory: M. Bender et al., NPA 723 (2003) 354
HFB + SLy4 M. Bender et al W.S. S. Ćwiok et al. ½-½ HFB + Gogny H. Goutte, priv. comm ½-½- ½-½
255 Lr – Recoil Tagging 209 Bi( 48 Ca,2n) 255 Lr
255 Lr – Recoil Decay Tagging
Comparison 255 Lr – 251 Md
Odd - neutron 253 No 151
Confirmed by F.P. Heßberger et al. E.P.J. A 22, 417 (2004) The ground state of 253 No is a neutron 9/2 - [734] state GREAT spectra from 207 Pb( 48 Ca,2n) 253 No γ rays electrons 253 No 1.7 min
Earlier Gammasphere+FMA experiment 207 Pb( 48 Ca,2n) 253 No – 0.5µb P. Reiter et al. PRL 95, (2005) 253 N o
JUROGAM + RITU Recoil-gated γ rays from 207 Pb( 48 Ca,2n) 253 No
253 N o Exp K=7/2 simulation K=9/2 simulation It is not 7/2+[624] band but 9/2-[734] 253 No
It is not 7/2+[624] band but 9/2-[734] 253 No
SACRED + RITU data In-beam conversion electrons from 207 Pb( 48 Ca,2n) 253 No K=7/2 simulation K=9/2 simulation Exp 9/2- [734] Indeed P. Butler et al.
Dynamic moment of inertia J (2)
Theory: M. Bender et al., NPA 723 (2003) 354
PERSPECTIVES Improved sensitivity for in-beam studies: Digital signal processing → Higher counting rate Digital signal processing → Higher counting rate Development of high-intensity beams In-beam gamma - electron concidences for SHE: Combined gamma-ray and electron spectrometer - SAGE
PERSPECTIVES Improved sensitivity for in-beam studies: Digital signal processing → Higher counting rate Development of high-intensity beams 50 Ti Pb → 256 Rf + 2n 50 Ti Pb → 256 Rf + 2n In-beam gamma - electron concidences for SHE: Combined gamma-ray and electron spectrometer - SAGE
In-beam γ rays from 208 Pb( 50 Ti,2n) 256 Rf – 12nb 700 recoils ↔ 25pnA, 1 week Simulation – a random bit of the 254 No experiment 256 Rf Z = 104
PERSPECTIVES Improved sensitivity for in-beam studies: Digital signal processing → Higher counting rate Development of high-intensity beams In-beam gamma - electron concidences for SHE: Combined gamma-ray and electron spectrometer - SAGE Combined gamma-ray and electron spectrometer - SAGE
SAGE UK investment
SAGE
Collaborating institutes
Thank you for your attention !
Moment of inertia