1 In-Beam Observables Rauno Julin Department of Physics University of Jyväskylä JYFL Finland

In - Beam γ n p p α γ 2

  , p, β, … e −,     prompt events = In-Beam delayed events tagged with Ge Array Focal plane Detectors Separator Beam Data Readout 3 Combination of In-Beam and Delayed Events Best resolution in gamma-ray spectroscopy

Sn Pb very neutron deficient heavy nuclei can be produced via fusion evaporation reactions  cross-sections down to 1 nb short-living alpha or proton emitters → tagging methods Nb 4 Example: In-beam probing of Proton-Drip Line and SHE nuclei

level energies, transition multipolarities, spins, parities 5

Yrast vs. non-Yrast All known energy levels in 116 Sn Only a very limited set of levels close to the yrast line can be seen Close to the valley of stability: Far from stability: 6

Example: in-beam spectroscopy at the extreme Pb 4 + → → → → 0 + α-α tagged singles in-beam γ-ray spectrum 92 Mo( 90 Zr,2n) 180 Pb, 10 nanobarn 7 P. Rahkila et al. Phys. Rev. C 82 (2010) (R)

Oblate Prolate 186 Pb 104 Spherical Energy-level systematics: Pb - isotopes Prolate Oblate Spherical Level systematics of even-A Pb nuclei N = Pb 8  Verification of shape coexistence

Oblate 4p-2h Spherical 0p-0h Prolate 6p-4h Energy-level systematics vs. Ground - state radia  Understanding of ground-state properties 9

Odd-A nuclei: Information about orbitals and deformation 10

Verification of prolate shape in 185 Pb Coupling of the i 13/2 neutron ”hole” to the prolate core 11 Strongly coupled band

Energy – level systematics: Coulomb-Energy Differences A=66 is the heaviest triplet of T = 1 bands up to 6+ N = Z TED = E x (T z = -1) + E x (T z = +1) - 2 E x (T z = 0) V = v pp + v nn - 2v pn Charge independence One-body terms cancel out TED=Triple Energy Differences Isospin non-conserving contribution is needed ! T = 1 band 66 Se

moment of inertia 13

Kinematical moment of inertia Dynamical moment of inertia = arithmetical average of over Quantal system Measured Basics 14

J vs. deformation Quadrupole deformed rigid rotor  not much dependent on deformation ! ~ SD band in 152 Dy ~ SD band in 193 Bi ~ fission isomer in Pu Fluid  strongly depends on deformation ! 15

J (1)  no Z = 104 shell gap Example: Nobelium region Why are 254 No and 256 Rf almost identical ? 16

Calculations 17

PROLATE OBLATE Rigid: J (1) ~ β Hydrodynamical: J (1) ~ β 2 → Need B(E2), Q t J (1) (rig) = 110 Example: Coexisting shapes in light Pb region 18

180 Pb Alignments: 180 Pb behaves like 188 Pb → Mixing with oblate structures Subtracting a reference  details 19

Subtracting a reference  details Alignments near N =104: Open symbols – Hg’s Filled symbols – Pb’s  Why Pb’s more scattered ? 20

level lifetimes, transition rates, quadrupole moments, deformation 21

Basics Quadrupole deformed nucleus: 22

Recoil distance Doppler-shift (RDDS) lifetime measurements (plunger). Combined with selective recoil-decay tagging method. In-beam lifetime measuremets 23

│Q t │ J (1)... for... for 194 Po 196 Po 186 Pb and 188 Pb Example: Lifetimes for shape coexisting levels in light Pb’s and Po’s Pb: │Q t │ → │β 2 │ = 0.29(5) for the ”pure” prolate states Po: │Q t │ → │β 2 │ = 0.17(3) for the oblate states - the ground state of 194 Po is a pure oblate 4p-2h state ? 24

Beyond-mean-field calculations by M. Bender et al. vs. the exp. data Theor. Theor. Exp Exp vs. Theory 25

J (1) identical for prolate intruder bands in N ~ 104 Pt, Hg and Pb ⇒ identical collectivity (Q t )? Example : Collectivity of the intruder bands in light Pt, Hg and Pb nuclei 26

oblate prolate Collectivity of the intruder bands in light Pt, Hg and Pb nuclei Is the collectivity really decreasing with decreasing Z ? 27

Δν=2 Δν= ν Testing the simple seniority picture: B(E2)-value systematics, N=122 Example: Experimental difficulties 8 + is long living  impossible to determine the lifetimes of the 6 +, 4 + and 2 + members of the multiplet 28

Comment Mass systematics vs. shape coexistence 29

Two-neutron separation energy systematics HgPt Why the smooth behaviour at N = 104 ? Scale !! 30

∆4∆4 Other mass filters needed to see the deviations Hg isotopes 31

Comment Interpretation of E0 transition rates 32

Interpretation: Weak mixing ( 10/90) between the spherical 0 + state and the deformed 2neutron-2hole intruder 0 + state (ß = 0,27) Comment : = 8.7 × is a small value for an E0 transition in light nuclei Does it make sense to apply such a simple model for such a weak E0 ? Example: 2neutron-2 hole intruders on the island of inversion 33

Example: 2neutron-2 hole intruders on the island of inversion The simple two-level mixing model:  !! Simple shell-model: ”Single-particle” value: = 40 × (A=44) (= E0 connecting 50/50 mixed 0 + states involving 2 protons occupying orbitals from different oscillator shells ) E0’s involving neutron excitations : (if no state-dependent monopole effective charge for neutrons) 34