ECT* Trento The Lead Radius. Precision measurements of nuclear ground state properties for nuclear structure studies. Klaus Blaum

Transcription

1 ECT* Trento The Lead Radius Precision measurements of nuclear ground state properties for nuclear structure studies Klaus Blaum

2 Outline Introduction, history and methods Principle of laser spectroscopy and mass spectrometry Setup and measurement procedure Precision measurements of nuclear ground state properties

3 Nuclear ground state properties ISOTOPE SHIFT Finite Size Effect Change of Charge Radius HYPERFINE STRUCTURE 1. Hyperfine Interaction nuclear spin 2. Magnetic Dipole HFS nuclear magnetic moment 3. Electric Quadrupole HFS spectroscopic quadrupole moment MASS Nuclear Binding Energy E BIN = ΔM c 2 Model-independent determination of ground state properties.

4 Part I High-precision laser spectroscopy

5 Principle of laser spectroscopy Resonant step-wise excitation of one (or more) electrons in the electron shell of the atom. Laser excitation/ionization The transition frequencies (wavelengths) are unique like a fingerprint for elements and isotopes. Varying the laser frequency allows to probe different isotopes and elements.

6 Collinear laser spectroscopy & β-nmr X + post acceleration crystal stopper lenses electrostatic optical detection deflection B T magnet scintillation detectors B = RF coil laser beam Δ 25 HFS of of Mg 25 Mg optical pumping region photons A(S 1/2 ) = 596.5(5) MHz I=1/2 m I = +1/2 hδν = gbμ N fine Doppler tuning voltage (V) m I = 1/2

7 Investigation of nuclear halos via nuclear mass (binding energy) and charge radii measurements! 6,8 He: P. Müller et al., Phys. Rev. Lett. 99, (2007) 11 Li: R. Neugart et al., Phys. Rev. Lett. 101, (2008) 11 Be: W. Nörtershäuser et al., Phys. Rev. Lett. 102, (2009) 17 Ne: W. Geithner et al., Phys. Rev. Lett. 101, (2008) isotope shift Halo = R Matter - R Charge 11 Li nuclear reactions

8 Be spectroscopy laser system Servo Dye Laser (Anticollinear) 20 m fiber Frequency Doubler Shaping Optics beam blocker Photodiode PMT Rubidium Clock Frequency Comb COLLAPS Retardation Be + - Beam Deflector beam blocker 20 m fiber Dye Laser (Collinear) Frequency Doubler I 2 FM-Iodine Lock Servo

9 11 Be nuclear charge radius rms charge radius (fm) A experiment Fermionic Molecular Dynamics No Core Shell Model from interaction cross section exp. Greens Function Monte Carlo Calculations W. Nörtershäuser et al., Phys. Rev. Lett. 102, (2009)

10 The simplified halo picture of 11 Be 11 Be n 10 Be W. Nörtershäuser et al., Phys. Rev. Lett. 102, (2009)

11 Collinear laser spectroscopy & β-nmr X + post acceleration crystal stopper lenses electrostatic optical detection deflection B T magnet scintillation detectors B = RF coil laser beam 31 Mg 10 β optical pumping region β-asymmetry HFS scan β-asymmetry β-nmr I=1/2 m I = +1/2 hδν = gbμ N Doppler tuning voltage (V) Radiofrequency (MHz) m I = 1/2

12 Spin and magnetic moment of 31 Mg 31 Mg (Z=12, N=19) 2p 3/2 1f 7/2 20 pf 2p 2h NMR 31 Mg, MgO 1d 3/2 2s 1/2 sd 1d 5/2 ν 8 μ Schmidt = 1.9μ N HFS 31 Mg II, D 2 Ground-state properties of 31 Mg μ = (15)μ N I = 1/2 G. Neyens et al., Phys. Rev. Lett. 94, (2005). M. Kowalska et al., Phys. Rev. C 77, (2008).

13 Part II High-precision mass measurements

14 Applications of precision masses High-accuracy mass measurements allow one to determine the atomic and nuclear binding energies reflecting all forces in the atom/nucleus. = N + Z + Z binding energy M Atom = N m neutron + Z m proton + Z m electron -(B atom + B nucleus )/c 2

15 A brief history of mass spectrometry Ca (T 1/2 = 440ms) 28 Si δe (A=100) Mass Uncertainty δm/m Mass Spectrographs RF Spectrometers Reaction Q ion cloud single ion PTMS 1 MeV 100 kev 10 kev 1 kev 100 ev 10 ev ev year SMILETRAP, MIT-TRAP (now at FSU), Seattle-TRAP, HD-TRAP CPT, ISOLTRAP, JYFLTRAP, LEBIT, SHIPTRAP

16 Principle of Penning trap mass spectrometry B q/m Cyclotron frequency: 1 q f c = B 2π m PENNING trap Strong homogen. magnetic field Weak electric 3D quadrupole field B Mean time of flight / μs Centroid: f c 1 q = B 2 π m 63 Ga T 1/2 = 32.4 s Excitation frequency ν RF / Hz f rf

17 Separation of isomeric states Isomerism in 68 Cu: kev IT 84% 16% 68 Cu 100% as produced by ISOLDE g: T 1/2 = 31.1 s m:t 1/2 = 3.75 min isolation of the 1 + ground state mean TOF (us) Zn isolation of the 6 - isomeric state Resolving power of excitation: R 10 7 Population inversion of nuclear states Preparation of an isomerically pure beam K. Blaum et al., Europhys. Lett. 67, 586 (2004) f exc (Hz)

18 Nuclear structure studies S p = B(Z,N) B(Z-1,N) S 2n = B(Z,N) B(Z,N-2) S(MeV) p Ho Tm N=128 shell closure deformation mass number First direct mass measurement beyond the proton dripline. C. Rauth et al., Phys. Rev. Lett. 100, (2008) M. Dworschak et al., Phys. Rev. Lett. 100, (2008) Investigation of shell closures, onset of deformation, collective effects. B. Cakirli et al., Phys. Rev. Lett. 102, (2009) D. Neidherr et al., Phys. Rev. Lett. 102, (2009)

19 The discovery of a new isotope, 229 Rn , 4:24 am D. Neidherr et al., Phys. Rev. Lett. 102, (2009)

20 132,134 Sn Magicity of N = 82 neutron shell gap 132 Sn Restoration of N = 82 gap M. Dworschak et al., Phys. Rev. Lett. 100, (2008)

21 Applications in astrophysics K. B. et al., Phys. J. 5, 35 (2006); H. Schatz et al., Europhys. News 37, 16 (2006) Conditions for an A=80 abundance peak Question 3 How How were were the the elements from from iron iron to to uranium situation made made 2007? (main (main question: r-process) with new 81 Zn mass with new 80 Zn mass M. Mukherjee et al., Phys. Rev. Lett. 93, (2004) D. Rodríguez et al., Phys. Rev. Lett. 93, (2004) V.-V. Elomaa et al., Phys. Rev. Lett. 102, (2009) S. Baruah et al., Phys. Rev. Lett. 101, (2008)

22 What has been done so far? Only Penning trap mass measurements! Stability of of SHE SHE Isospin Symmetry Pairing Exotic Exotic decays Fundamental Interactions rp-process rp-process r-process r-process Magic Magic Numbers Shell Shell Evolution Halos Halos and and Skins Skins

23 Summary Precision atomic physics techniques play an important role in nuclear structure studies! Precise determination of atomic and nuclear ground state properties Investigation of nuclear halos Test of nuclear mass models Nuclear structure studies Weak interaction studies Reliable calculations in nuclear astrophysics need precision nuclear ground state data like masses Tests of fundamental symmetries and interactions For Bob!

24 Thanks Thanks a lot for the invitation and your attention! klaus.blaum@mpi-hd.mpg.de WWW: