1 undressing (to fiddle the decay probability) keV gamma E0, 0 + ->0 + e - conversion decay E x =509 keV, T 1/2 ~20 ns Fully stripping the nucleus of its atomic electrons (in-flight) ‘switches off’ the electron conversion decay branches. Result is that the bare nuclear isomeric lifetime is increased compared to ‘atomic’ value. (important in explosive stellar scenarios).

2 74 Kr isomer from 92 Mo fragmentation at GANIL. 456 keV 2 + ->0 + transitions decays (a) too fast (500 ns flight time) & (b) too slow for measured value of 2 + state (~25 ps) ?

3 C. Chandler et al. Phys. Rev. C61 (2000) Ge 69 Se 76 Rb 92 Mo fragmentation on nat Ni target

4 Two level mixing The gamma-rays emitted from nuclear reactions exhibit angular distributions that can be expressed as follow: Q 2,Q 4 : Solid angle corrections, due to the finite size of the detectors

5 Backbending can be interpreted as the crossing of two bands The ‘G’ band (Ground state) is a fully paired configuration The ‘S’ band (Super or Stockholm) contains one broken pair Band Crossings

6 Backbending

7 Systematics of B(E2)s In near stable and proton rich nuclei there is a fixed relationship between B(E2) and E2 + “GRODZINS RULE” However, in neutron rich nuclei, this should break down, and the link between B(E2) and deformation WILL be more complicated.

8

9

10

11 Can not use fusion-evaporation reactions to study high-spin states in beta-stable and neutron-rich systems. Z N E beam ~15-20% above Coulomb barrier beam target (i) (ii) (iii) Deep inelastic collisions

12 Projectile Fragmentation Reactions hotspot Excited pre-fragment Final fragment projectile target Energy (velocity) of beam > Fermi velocity inside nucleus ~30 MeV/u Can ‘shear off’ different combinations of protons and neutrons. Large variety of exotic nuclear species created, all at forward angles with ~beam velocity.

13 Nuclear Reactions – very schematic!  Gamma-ray induced no Coulomb barrier  Neutron induced low-spin states no Coulomb barrier  Light charged particles, e.g. p, d, t,  Coulomb barrier low-spin states (“capture”) (“fast”) Near the line of stability

14 DCO Ratios  is the angle between two planes opened by each detector and the beam axis probability (intensity) for this specific configuration, e.g. the intensity of transition  , determined in detector 2, gated on the transition   in detector 1

15 DCO Ratios  is the angle between two planes opened by each detector and the beam axis probability (intensity) for this specific configuration, e.g. the intensity of transition  , determined in detector 2, gated on the transition   in detector 1

Hf 16 +, 4-qp Isomer

17 Courtesy to John Becker, LLNL MeV 31 y  28 g - boils 120 t of water  1 g - equivalent to 650 lbs. of TNT

18 Some Applications SPIEGEL ONLINE August 2003, 15:27 Pentagon-Pläne Handliches Höllenfeuer Das US-Militär entwickelt einen neuartigen Nuklearsprengstoff, der schon in kleinsten Mengen ungeheure Vernichtungskräfte entfesseln, zugleich aber auch in Kleinstwaffen eingesetzt werden kann. Experten warnen bereits vor einem neuen globalen Wettrüsten. Nuklearexplosion: Isomere können in großem und kleinem Maßstab eingesetzt werden New Scientist, 2003

19 Triggering of 178m Hf using X-rays Texas/AFRL/SNL Collaboration/Phys. Rev. Lett. 82 (1999) 695

20 Triggering of 178m Hf using X-rays – cont. ANL/LANL/LLNL /Phys. Rev. Lett. 87 (2001)

21 Can K-Mixing explain the results by Collins et al? Texas/AFRL/SNL Collaboration Phys. Rev. Lett. 82 (1999) 695 Before the mixing I ,K 1 I ,K 2 and K 2 >K 1 After the mixing  |I ,K 1 > -  |I ,K 2 >  |I ,K 1 > +  |I ,K 2 >  two levels with the same I  and <90 keV above the isomer  must have I=15,16 or 17, e.g. high spin  must have very different K  V is very small (~eV!) V

Hf ANU Experiment Incomplete fusion  n   9 Be 5 He 176 Yb 178 Hf

Hf ANU Experiment - cont.