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