S1155 Ground State Moments of Lithium Status and Recent Results

Transcription

1 S1155 Ground State Moments of Lithium Status and Recent Results, 2. June 2010

2 Lithium charge radii RMS charge radii of Li isotopes Data taken from: Sánchez et al. PRL 96, (2006) RMS charge radii of 9 Li and 11 Li Picture taken from: Nörtershäuser & Müller PiuZ 40, 96 (2009)

3 β-nqr technique β detected Nuclear Quadrupole Resonance β-decay asymmetry: electron emitted preferentially in direction of nuclear spin at time of decay (for positive A) Picture taken from: Salman et al. Phys Rev B 70, (2004)

4 Interaction of beam with host crystal magnetic dipole term electric quadrupole term with zero-magnetic field and insulator crystal with cubic structure: only one fit parameter: centroid

5 Spin polarisation polarisation region (via optical pumping) β-nqr spectrometer 28 kev ion beam from ISAC Picture taken from: Kiefl et al. Phys B 326, 189 (2003) β-nmr spectrometer

6 Zero field spectrometer ion beam light guides to PM tubes from left detectors left detectors (L) Helmholtz coils

7 SrTiO 3 : host crystal Lattice structure empty Al 2 O 3 SrTiO 3 Au

8 RF resonance frequencies 8 Li 9,11 Li ratio of resonance RF frequencies:

9 β-nqr of 8,9 Li in SrTiO T = 300 K (2009) literature values for ratio of quadrupole moments:??? Data taken from Arnold et al. Phys Lett B 281, 16 (1992) Data taken from Borremans et al. Phys Rev C 72, (2005) 8 Li yield station: 4.1 e 7 s -1 experiment: ~ 2.5 e 6 s -1 ~ 2.5 e 5 cps 9 Li yield station: 1.6 e 6 s -1 experiment: ~ 6.5 e 4 s -1 ~ 6500 cps

10 Results (2009) Observed resonance frequencies Ratio of quadrupole moments with a systematic uncertainty of Borremans (Phys Rev C 72, (2005)) This is in good agreement with the ratio calculated from Borremans but with an improved uncertainty.

11 Never a failure always a lesson! or: What we learnt from the previous experiment stabilise crystal temperature use LN2 for cooling power from the beginning 2. real-time logging of B see changes in B instantaneously

12 Real-time B-field logging Hall probe in close proximity to implantation region Zero B Continuous B-field logging test move crane to refill LN2

13 β-nqr of 8,9 Li in SrTiO T = 295 K 8 Li 9 Li yield station: 8.2 e 8 s -1 experiment: ~ 6.0 e 6 s -1 ~ 6.0 e 5 cps yield station: 1.2 e 7 s -1 experiment: ~ 4.7 e 6 s -1 ~ 4.7 e 5 cps

14 Temperature dependency of ν Q 8 Li 9 Li

15 Results for 8,9 Li Observed resonance frequencies Ratio of quadrupole moments with a systematic uncertainty of We improved our own measurement from 2009!

16 Baseline correction negative helicity Asymmetry baseline averaging positive helicity RF Frequency

17 11 Li (low-field) NMR yield station: 1100 s -1 experiment: ~400 s -1 ~40 cps 24 h (total 11 Li NMR data) B = 9.25 G resonance at ~17.3 khz Is this good enough for 11 Li NQR in B=0?

18 11 Li NQR?!? yield station: 1100 s -1 experiment: ~ s -1 ~20 40 cps 48 h (total 11 Li NQR data) binning factor: 2 resonance at ~318 khz agrees with Neugart et al. PRL 101, (2008)

19 Summary first time: β-nqr TRIUMF used for nuclear physics first time: determination of ratio of quadrupole moments in B=0 for radioactive isotopes showed β-nqr in B=0 is suitable method used 8 Li to zero B and 8,9 Li for systematic studies measured Q 9 /Q 8 in B=0 with significantly improved uncertainty observed 11 Li low-field NMR signal agreement with literature observed 11 Li NQR signal in B = 0 agreement with literature

20 Thank you! A. Voss, M.R. Pearson, J. Billowes, F. Buchinger, K.H. Chow, J.E. Crawford, S. Daviel, M.D. Hossein, R.F. Kiefl, C.D.P. Levy, W.A. MacFarlane, E. Mané, G.D. Morris, T.J. Parolin, H. Saadaoui, Z. Salman, M. Smadella, Q. Song, D. Wang