Resonant laser ionization of Po at ISOLDE

Transcription

1 Resonant laser ionization of Po at ISOLDE IKS, KULeuven T.E. Cocolios, M. Huyse, Yu. Kudryavtsev, P. Van Duppen ISOLDE, CERN V.N. Fedosseev, K. Johnston, B.A. Marsh IPNO, Orsay S. Franchoo Johannes Gutenberg Universität, Mainz M. Seliverstov PNPI, Gatchina A. Ionan

2 Outline Polonium laser ionization... JRA06...subtask 2.1 Possible use of laser ionized beams of polonium at ISOLDE... JRA06...subtask 2.2 α decay... δ<r 2 >... In-source laser spectroscopy...

3 Po excitation schemes 8.42eV 6p 3 7p 5 P 2 510,6 nm nm 538,89 nm 532,34 nm 6p 3 8p? 12 6p 3 8p? 10 J=1 or 2 6p 3 7s 3 S 1 6p 3 7s 5 S 2 255,8 nm 245,01 nm 6p 4 3 P 2

4 Transition saturation tion First scheme Second scheme On-line test from Nov.2006

5 Po yields On-line test from Nov.2006

6 Odd isotope nuclear spectroscopy More precise conversion coefficients in intruder states in Pb Identification of cross-over decays in 193,195,197 Po Mass derivation <= from Pb mass and Po Q a value => E0-M1-E2 transition strength K. Van de Vel et al., PR C 65, p , (2002) A.N. Andreyev et al., PR C 66, p , (2002) + identification of new highly non-yrast levels in 189,191,193 Pb + study of isomerically separated beams Some of these studies can even be performed parasitically of the HFS measurements (α γ studies)...

7 δ<r 2 > around z=82 H. De Witte et al. PRL 98 (2007) p Hg = G. Ulm et al., Zeit. fur Phys. A 325, 247 (1986), Pt = Le Blanc F. et al., Phys. R ev. C 60, (1999), Pb = De Witte H. et al., PRL 98, (2007), Po = Kowalewska D. et al, Phys. Rev. A 44, 1442R (1991)

8 In-source laser spectroscopy 60kV Standard laser ionization One of the resonant step on narrow width Detection of the particles Yield vs. laser frequency gives the resonance curve

9 In-source vs in-flight Doppler broaden sample from a hot source results in wide spectra Why bother with insource then?? G.Neyens, C OLLAP S presentation Doppler compressed sample from an accelerated beam results in narrow, almost Doppler-free spectra

10 In-source vs in-flight In flight spectroscopy + Doppler compression of fast-beam (improved resolution) - Creation of the beam (external ion source) - Manipulation for detection (neutralisation, polarisation, fluorescence,...) - High yield required (or work with additional equipment such as an RFQ cooler) In source spectroscopy Appropriate for heavy elements Po detection by α-decay - Doppler broadened sample (thermal distribution of the source) + No need to create a beam (spectroscopy is the source) + Simple detection of the flux of ions (beam current, nuclear spectroscopy,...) + Sensitive to extremely low yields (few ions per second for 182 Pb)

11 Experimental layout RILIS Windmill 195 Po Counts Energy [MeV] H. De Witte et al., P R L 98, (2007)

12 Isotope shift: an example H. De Witte et al., PR L 98, (2007)

13 Recall on Isotope Shift Shift in the electronic levels from one nucleus to the next of the same element (isotopes, isomers) Interaction between a nucleus wavefunction and an s-electron Shift in the frequency of the transition F r 2 Mass Shift

14 Remember... Po excitation schemes 8.42eV 6p 3 7p 5 P 2 510,6 nm nm 538,89 nm 532,34 nm 6p 3 8p? 12 6p 3 8p? 10 J=1 or 2 6p 3 7s 3 S 1 6p 3 7s 5 S 2 255,8 nm 245,01 nm 6p 4 3 P 2

15 ISOLDE RILIS Bruce Marsh, The IS OLDE R ILIS

16 α Po detection On-line test from Nov.2006

17 Conclusions and outlook Polonium is now available with two very efficient laser ionization schemes from RILIS-ISOLDE. First proposed experiment is on the mean-squared charge radii of the neutron deficient polonium isotopes. IS456: 19 shifts for the study of the even-even isotopes July 19-25, 2007, at ISOLDE. Electronic factors required to extract the mean-squared charge radii from the isotope shifts. Odd-even isotopes and nuclear spectroscopy to follow in the coming years.

18 Polonium δ<r 2 > collaboration IKS, KULeuven T.E. Cocolios, M. Huyse, Yu. Kudryavtsev, J. Van de Walle, P. Van Duppen ISOLDE, CERN V.N. Fedosseev, B.A. Marsh IPNO, Orsay S. Franchoo, F. Le Blanc Johannes Gutenberg Universität, Mainz G. Huber, M. Seliverstov University of Manchester, Manchester J. Billowes, P. Campbell, E. Mané University of Sevilla, Seville I. Mukha Institut Laue Langevin, Grenoble U. Köster TRIUMF, Vancouver BC A.N. Andreyev Petersburg Nuclear Physics Institute, Gatchina A.E. Barzakh, D. Fedorov, A. Ionan, Yu. Volkov University of Richmond, Richmond VA S.R. Lesher Kassel University, Kassel S. Fritzsche