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Collinear resonance ionization spectroscopy of neutron rich 218m,219,229,231 Fr isotopes

Collinear resonance ionization spectroscopy of neutron rich 218m,219,229,231 Fr isotopes. Ivan Budinčević P hd student – nuclear moments group, IKS, KU Leuven Supervisor: Gerda Neyens. ISOLDE Workshop, 27.11.2013. Contents. Physics motivation The CRIS experimental setup at ISOLDE

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Collinear resonance ionization spectroscopy of neutron rich 218m,219,229,231 Fr isotopes

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  1. Collinear resonance ionization spectroscopy of neutron rich 218m,219,229,231Fr isotopes Ivan Budinčević Phd student – nuclear moments group, IKS, KU Leuven Supervisor: GerdaNeyens ISOLDE Workshop, 27.11.2013

  2. Contents • Physics motivation • The CRIS experimental setup at ISOLDE • Experimental results and discussion • Conclusions

  3. Fr physical motivation • 218,219Fr both exhibit alternating parity bands [1,2] which are generally associated with the presence of octupole deformations [3]. • The observed inversion of odd-even staggering of charge radii for 221-225Fr [4] has been associated with octupole deformations. Neutron-rich Fr isotopes [1] M. E. Debray et al., Phys. Rev. C 62, 024304 (2000), [2] C.F. Liang et al., Phys. Rev. C 44, 676 (1991), [3] R.K. ShelinePhys.Lett. 197B, 500 (1987), [4] A. Cocet al., Phys.Lett. 163B, 66 (1985)

  4. Alternating parity band 218Fr [1] M. E. Debray et al., Phys. Rev. C 62, 024304 (2000)

  5. Parity doublet band 219Fr [2] C.F. Liang et al., Phys. Rev. C 44, 676 (1991)

  6. Laser spectroscopy • Ion detection continuum ionization potential ν2 second step laser photon excited state Hyperfine splitting ν1 laser photon ground state

  7. Laser spectroscopy • Ion detection continuum ionization potential ν2 second step laser photon excited state Hyperfine splitting ν1-+ Δ ν laser photon ground state

  8. Laser spectroscopy • Ion detection continuum ionization potential ν2 second step laser photon excited state Hyperfine splitting ν1-- Δ ν laser photon ground state

  9. Ion detectioncharacteristics • No losses due to solid angle coverage and scattered laser light - > higher detection efficiency compared to photon detection • Ion beam transport efficiency is an important factor • Neutralization efficiency (Charge Exchange) • High vacuum is required ~ 10-8 – 10-9 mbar

  10. The Collinear Resonant Ionization Spectroscopy (CRIS) beamline

  11. The Collinear Resonant Ionization Spectroscopy (CRIS) beamline

  12. The Collinear Resonant Ionization Spectroscopy (CRIS) beamline

  13. The Collinear Resonant Ionization Spectroscopy (CRIS) beamline

  14. The Collinear Resonant Ionization Spectroscopy (CRIS) beamline

  15. The Collinear Resonant Ionization Spectroscopy (CRIS) beamline

  16. The Collinear Resonant Ionization Spectroscopy (CRIS) beamline

  17. The Collinear Resonant Ionization Spectroscopy (CRIS) beamline

  18. The Collinear Resonant Ionization Spectroscopy (CRIS) beamline

  19. The Collinear Resonant Ionization Spectroscopy (CRIS) beamline

  20. Laser system 1064nm 422nm

  21. Fr experimental results – reference isotopes Fr ionization scheme

  22. Fr experimental results – 218mFr, 219Fr T1/2(218mFr) = 0.022(5) s [5], scan made in 44min T1/2(219Fr) = 0.0267(6) s [5], scan made in 33min [5] G.T. Ewan et al., Nucl. Phys. A380 (1982) 423

  23. 218mFr half-life 218Fr alpha-particle energy spectrum Half-life determination [6] K. M. Lynch and K. Flanagan, Laser assisted nuclear decay spectroscopy: A new method for studying neutron-deficient francium, Ph.D. thesis, Manchester U. (2013)

  24. Fr experimental results – 229Fr, 231Fr

  25. Characteristics of the region of reflection asymmetry – octupole deformations • Quadrupole – octupole shapes for β2 = 0.6, β3µ = 0.35, taken from [7] Butler Rev.Mod. Phys. 68 (1996) 349 µ = 0 µ = 1 µ = 2 µ = 3

  26. Characteristics of the region of reflection asymmetry – spectroscopic properties • Parity doublet bands • Charge radii/isotope shifts • Ground state spins and magnetic moments • Coriolis matrix elements • Spectroscopic factors • Enhanced E1 transition probabilities • [3] R.K. ShelinePhys.Lett. 197B, 500 (1987)

  27. Characteristics of the region of reflection asymmetry – spectroscopic properties • Parity doublet bands • Charge radii/isotope shifts • Ground state spins and magnetic moments • Coriolis matrix elements • Spectroscopic factors • Enhanced E1 transition probabilities • [3] R.K. ShelinePhys.Lett. 197B, 500 (1987)

  28. Relative mean-square charge radii • The large theoretical errors stem from the calculated uncertainties for the Field and mass shift constants for Ra [9,10] [4] A. Cocet al., Phys.Lett. 163B, 66 (1985), [8] K. Wendt et al., Z. Phys. D 4, 227 (1987), [9] V.A. Dzubaet al., Phys.Rev. A 72, 022503 (2005), [10] L.W. Wansbeeket al., Phys.Rev. C 86, 015503 (2012)

  29. Relative mean-square charge radii Taken from [9] [4] A. Cocet al., Phys.Lett. 163B, 66 (1985). [8] K. Wendt et al., Z. Phys. D 4, 227 (1987), [11] A. Coc et al., Nuclear Physics A468 (1987) 1

  30. Relative mean-square charge radii • OES effect of pairing on the collective potential . • Normal OES – smaller <r2> for odd N nuclei compared to the average of their even N neighbors. [12] S. Ahmad et al., Nuc. Phys. A 483,244 (1988).

  31. Relative mean-square charge radii • Inverted odd even staggering for 221-225Fr (N=135-138) and 221-226Ra (N=133-138) • Our results for δν(219,229Fr) will add the points for D(N; δν) (220,228Fr) (N=133,141) to this plot [4] A. Cocet al., Phys.Lett. 163B, 66 (1985). [8] K. Wendt et al., Z. Phys. D 4, 227 (1987), [11] A. Coc et al., Nuclear Physics A468 (1987) 1

  32. 220-228 Fr interpretations from literature • The spin sequence for 220,222,224,226,228Fr was reproduced by [13] including octupole deformations. • Magnetic dipole and electric quadrupole moments of 224,226,228Fr were qualitatively well reproduced by [14] without octupole deformations • 223Fr was studied by [15] and they concluded the experimental data agreed with the theoretical predictions of a reflection asymmetric rotor model. • [16] concluded octupole correlations do play a role in 225 Fr, but there is no stable deformation. • 227Fr is considered to be a transitional nucleus [17] [13] RK Sheline. Octupole deformation in odd-odd nuclei. Phys. Rev. C, 37(1)1988, [14] C. Ekstrom et al., Phys. Scr. 34:624-633,1986.[15] W. Kurcewicz, et al., Nuc. Phys A, 539(3)1992. [16] D.G. Burke, W Nuc. Phys.A,612(1)1997. [17] W. Kurcewicz et al., Nucl. Phys. A, 621(4)1997.

  33. Magnetic dipole moments and nuclear g factors particle-hole excitations protons i 13/2 i 13/2 f 7/2 f 7/2 h 9/2 h 9/2 Z = 82 Z = 82 s 1/2 s 1/2 d 3/2 d 3/2

  34. Magnetic dipole moments and nuclear g factors protons neutrons 2i 13/2 1j 15/2 1f 7/2 1i 11/2 1h 9/2 2g 9/2 Z = 82 N = 126 3s 1/2 3p 1/2 2d 3/2 2h 11/2 221Fr -> N = 134

  35. Magnetic dipole moments and nuclear g factors particle-hole excitations neutrons i 13/2 1j 15/2 f 7/2 1i 11/2 h 9/2 2g 9/2 Z = 82 N = 126 s 1/2 3p 1/2 d 3/2 2h 11/2 227Fr -> N = 140

  36. Conclusions • Collinear resonance ionization spectroscopy was used to measure the hyperfine structure of the 218m,219,229,231Fr isotopes. • The extracted magnetic dipole moments and relative mean-square charge radii will provide information about the nuclear structure of these isotopes, lying on the borders of the region of reflection asymmetry.

  37. Conclusions • The isotope shifts will show if these isotopes do exhibit inverted odd-even staggering, which has been associated with the presence of reflection-asymmetric nuclear shapes. • The magnetic dipole moments will provide information of the orbital occupancy of the valence nucleons. • Information about the nuclear spin for 229,231Fr may be attained.

  38. Thank you for your attention

  39. Extra slides

  40. Odd-even staggering Y factor

  41. Nuclemon

  42. Nuclemon

  43. Quadrupoleoctupoleshapes • where αλμ are deformation parameters, c(α) is determined from the volume conservation condition and R0=roA1/3 • α30=β30 ; α3-m=(-1)mα3m=β3m/2; β3m=0.35

  44. Conditions for static octupole deformations Butler Rev.Mod. Phys. 68 (1996) 349

  45. Parity mixing • The pairing plus multipolehamiltonian • where the first term on the right-hand side is the spherical shell-model potential, the second term represents a long-range separable multipole-multipole force generating the collective motion, Hpairis the pairing Hamiltonian, and j stands for the set of quantum numbers (n, l ,j). • Qλµis the multiple operator • and fλ(r) is the radial form factor

  46. Parity mixing • A coupling between single-particle states of opposite parity is produced by the octupole-octupole (λ=3) residual interaction. • The necessary condition for the presence of low-energy octupole collectivity is the existence, near the Fermi level, of pairs of orbitals strongly coupled by the octupole interaction. • For normally deformed systems the condition for strong octupole coupling is satisfied for particle numbers associated with the maximum ΔN=1 interaction between the intruder subshell (l ,j) and the normal-paritysubshell (l - 3, j - 3)

  47. Parity mixing Nuclear spherical single particle levels with the most important octupole couplings highlighted

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