Deep-Inelastic and Multinucleon Reactions with Discrete Gamma  ray Spectroscopy: A Brief Review Paddy Regan Dept. of Physics University of Surrey, UK

Physics of neutron-rich nuclei is the evolution of shell structure related to large energy gaps in the nuclear single-particle spectrum. Reasons to study neutron-rich nuclei include: 1)Evolution of collective modes (vibrations, rotations, superdef ?) from spherical states by altering position in (N, Z, I , E x ) space. 2)Identification of specific orbitals, e.g. via isomers; g-factors; B(E2:I->I-2); shell model, seniority, Nilsson schemes etc. 3) Identifying new nuclear ‘exotica’, e.g.,  -/proton/  -decaying states; new symmetries (e.g.,  32 ), shell closures, shape changes..etc.

(Some) DIC basics. –Thick or thin targets ? (I , E x,N, Z) ; isomer gating etc. Thin target multi-nucleon transfer reactions: –Neutron-rich C nuclei (Berlin BRS). –N~20, Island of Inversion. –N=32,34 (sub)-shell closures, Se (Z=34, N=50). – 48 Ca magic number(s). –N=50 robustness and shell closure. –Rotation/vibration evolution in A~100. – 132 Sn region Seniority I  =10 + isomers, h 11/2 neutron hole migration ? Surface diffuseness, weakening of N=82 shell ? – A~ K-isomerism and nuclear shape symmetry. – 208 Pb at high spins; octupole collective vibrations etc. –U, Th octupole states, (very) high-j intruders (k 17/2 etc.) –DIC with RIBs ( 24 Ne beam at GANIL) –TIARA (d,p) etc. in inverse kinematics….

Courtesy, Bogdan Fornal

Courtesy, Bogdan Fornal

R.Broda et al., Phys. Rev. C49 (1994)

W. Krolas et al., Nucl. Phys. A724, 289 (2003). 208 Pb 64 Ni

Advantages and limitations of  -ray thick target measurements with DIC ADVANTAGES Gamma rays from all reaction products Gamma rays from the stopped nuclei – narrow lines – easy analysis of  coincidences Detection of cross-coincidences – some potential for identification LIMITATIONS Gamma spectra very complicated (hundreds of sources) Gamma rays from the short lived states smeared out by the Doppler effect (emitted before a product is stopped) Difficulties of identifications without a starting point. Angular distribution of  rays almost isotropic

186 W 3.5 MeV, >3 ms, 16 + Off-beam singles, 7h Total singles, 15 min. Deep-inelastic reactions For K-Isomers with 238 U beams Out-of-beam condition yields only lines from the new isomers. Out-of-beam condition yields only lines from the new isomers. Without an off-beam timing condition, only Coulomb excitation lines are seen. Without an off-beam timing condition, only Coulomb excitation lines are seen. 238 U at 1600 MeV 186 W (16 mg cm -2 ) μs →ms beam pulsing Argonne/Notre-Dame array of 12 Ge dets. 1.5 MeV, 18 μs, 7 – Courtesy, Carl Wheldon

z x y    

M. Simon et al., Nucl. Inst. Meth. A452, 205 (2000) BLF TLF beam  tlf  tlf  blf  blf Ge TOF ~5-10 ns. ns-  s isomers can de-excite in be stopped by CHICO position detector. Delayed  s can still be viewed by GAMMASPHERE. Rochester Group

100 Mo MeV GAMMASPHERE + CHICO PHR, A.D. Yamamoto et al., AIP Conf. Proc. 701 (2004) p329

PHR, A.D.Yamamoto et al., Phys. Rev. C68 (2003) Can see clearly to spins of 20ħ using thin-target technique.

nano to microsecond isomer tagging ?

Isomer gating very useful in DIC experiments. PHR, A.D.Yamamoto et al., Phys. Rev. C68 (2003)

Wilczynski (‘Q-value loss) Plot A.D.Yamamoto, Surrey PhD thesis (2004)

Can we use the data from the CHICO+Gammasphere expt. to understand the ‘DIC’ reaction mechanism ? A wide range of spins & nuclei are observed.

What about the spin input ?

R. Bock et al., Nukleonika 22 (1977) 529

+2p -2n +2n Fold distributions highlight different reaction mechanisms PHR, A.D.Yamamoto et al., Phys. Rev. C68 (2003)

TLFs BLFs elastics PHR, A.D.Yamamoto et al., Phys. Rev. C68 (2003)

Emission angle of TLFs can give information/selection on reaction mechanism (and spin input).

198 Pt Xe, 850 MeV J.J. Valiente-Dobon, PHR, C.Wheldon et al., Phys. Rev. C69 (2004)

J.J. Valiente-Dobon, PHR, C.Wheldon et al., Phys. Rev. C69 (2004) Temporal separation can clearly identify ‘prompts’ and isomer decays 136 Xe Pt

N/Z compound nano and microsecond isomers on gated 198 Pt+ 136 Xe with GAMMASPHERE+CHICO DIC J.J. Valiente-Dobon, PHR, C.Wheldon et al., Phys. Rev. C69 (2004)

136 Xe+ 198 Pt Target-like fragment isomers J.J.Valiente-Dobon, PHR, C.Wheldon et al., PRC69 (2004) W 185 Re 191 Os 192 Os 195 Os 192 Pt 198 Pt 193 Au

 information and lifetime determination of 195 Os isomer decay

New isomer in 195 Os identified in GSI projectile fragmentation confirmed ‘in-beam’ CHICO+GAMMASPHERE  data. Dobon, Wheldon, Regan et al., M.Caamano, P.M.Walker, PHR et al., Eur. Phys. J. A (2005)

J.J.Valiente-Dobon, PHR, C.Wheldon et al., PRC69 (2004) Xe+ 198 Pt reaction beam-like fragment isomers. 131 I 133 I 128 Te 130 Te 136 Xe 132 Xe 138 Ba 137 La

J.J. Valiente-Dobon, PHR, C.Wheldon et al., Phys. Rev. C69 (2004) N=80 isotone 10 +

N=80 isotonic chain, 10 + isomers, ( h 11/2 ) -2 I=10 + Q. Why does E x (10 + ) increase while E(2 + ) decreases ? 91(2) ns

Energy of N=80 I  =10 + isomers correlates with energy increase of 11/2 - single neutron hole in N=81 isotones. Increase in 10 + energy, plus expansion of proton valence space means 8 + yrast state now (mostly) NOT ( h 11/2 ) -2 for Z>54 N=81 N=80 E x, I  =11/2 - E x, I  =10 Valiente-Dobon, PHR, Wheldon et al., PR C69 (2004)

Pair Truncated Shell Model Calculations (by Yoshinaga, Higashiyama et al. Saitama) predict yrast 8 + in 136 Ba no longer mostly ( h 11/2 ) -2 but rather, (  d 5/2 ) 2 (  g 7/2 ) 2

BRS+EUROBALL Energy Z Carbon gate Doppler correction from energy in BRS Add-back included 18 O at 90 on 9 Be (98 μg.cm -2 ) 18 O at 90 MeV on 9 Be (98 μg.cm -2 ) BRS  = ±12.5° → ±45.5° BRS  = ±12.5° → ±45.5° Euroball: 15 clusters, 26 clovers (209 crystals) Euroball: 15 clusters, 26 clovers (209 crystals) Unique-Z id., position to 1 mm, energy of recoil Unique-Z id., position to 1 mm, energy of recoil Particle-γ, particle-γ-γ and particle-particle-γ-γ Particle-γ, particle-γ-γ and particle-particle-γ-γcoincidences Courtesy, Tzany Kokolova

S. Lunardi, Acta. Phys. Pol. B36 (2005) 1301 CLARA

S. Lunardi, Acta. Phys. Pol. B36 (2005) 1301 A. Gadea et al., J. Phys. G (2005) in press

S. Lunardi, Acta. Phys. Pol. B36 (2005) 1301

H He Li Be B C N O F Ne Na Mg 24 Ne Deep Inelastic Collision reaction with light exotic beam Population of exotic Ne-F-O isotopes Report of the E421S experiment (spokeperson F.Azaiez): aim of the experiment cross section measurements  spectroscopy Ne-O-F DIC with RIBs! A new era ? courtesy, Giovanna Benzoni

Report of the E421S experiment: Experimental details reaction: MeV/A Pb (10.9 mg/cm 2 ) 24 Ne 5+, I beam ~ pps beam on target for 7 days setup: Vamos + EXOGAM 45° EXOGAM 11 detectors (2 without Compton shield) Typical count rates: Ions: 30/min  Total Ion counts: 7*24*60*30 =  cross section determination is feasible Ion-gamma coincidence 70/h  Total Ion-gamma coinc. 7*24*70 =  only spectroscopy of inelastic ch. courtesy, Giovanna Benzoni

Report of the E421S experiment: very preliminary spectra ID-plot E  E (a.u) Ne F O Na E (a.u.) Ne (inelastic) 3 days of statistics (~ 1/2) Conditions: -Si-gamma coincidence - Prompt gamma peaks - calculated v/c Analysis in progress Working on mass separation courtesy, Giovanna Benzoni

Report of the E421S experiment: future F Ne 24 Ne ~ 500 mb 26 Ne ~ 80 mb (2n pick up) 23 F ~ 20 mb (1p removal) Beam intensity required to study weaker channels to get to more exotic Ne isotopes  ~ 10 6 to get to F  to get to O  ~ 10 7 courtesy, Giovanna Benzoni

TIARA courtesy, Wilton Catford

Experimental Results for 24 Ne(d,p) 25 Ne Transfer with TIARA TIARA 25 Ne (d,p) 10 MeV/u Courtesy, Wilton Catford

DIC physics…. –Neutron-rich C nuclei (Berlin BRS). –N~20, Island of Inversion. –N=32,34 (sub)-shell closures, Se (Z=34, N=50). – 48 Ca magic number(s). –N=50 robustness and shell closure. –Rotation/vibration evolution in A~100. – 132 Sn region Seniority I  =10 + isomers, h 11/2 neutron hole migration ? Surface diffuseness, weakening of N=82 shell ? – A~ K-isomerism and nuclear shape symmetry. – 208 Pb at high spins; octupole collective vibrations etc. –U, Th octupole states, (very) high-j intruders (k 17/2 etc.) –DIC with RIBs ( 24 Ne beam at GANIL) –TIARA (d,p) etc. in inverse kinematics….