Laser pumping of ions in a cooler-buncher The University of Manchester, UK The University of Birmingham, UK At the JYFL accelerator facility, Finland

Collinear laser spectroscopy LaserIon source (cooler) PMT Gates +40kV +/- ≈ 3kV Platform ∙ Isotope shifts ∙ Hyperfine splitting Magnetic moment <β2><β2> Quadrupole moment δ δσ Size Shape Diffuseness Fast and sensitive δ<β22>δ<β22>

The JYFL IGISOL ● Fast extraction (~1ms) ● Chemically non-selective

Reduced peak skewing The RF cooler-buncher z V z He buffer gas End plate Energy spread 100eV 1eV Emittance = 3п.mm.mrad Less spectral broadening Better laser-ion overlap

Bunching and laser spectroscopy Counts hours 48 minutes 8000 ions/s 2000 ions/s 100V z End plate potential Accumulate Release Before After PMT 15µs gate Backgroundeg. 200ms accumulation = 20µs gate width suppression ~10 4

New results: multi QP isomers Raghavan'89 Multi-QP states Reduced pairing Less diffuse or more rigid Linked to origins of odd-even staggering?

Yttrium results J = 0J = 1 electronic transition ⇒ 3 peaks for each nuclide (maximum) gives the centroid, μ and Q One resonant photon per 2000 ions Efficiency:- Shape change at N=59 98m is well deformed

Yttrium charge radii

Problem 1: Spin determination Similarly with A=102 and A=100 98m

Problem 2: “Collapsed” ground states Difficult to resolve underlying peaks and ordering Spin ½ Spin 2 Spin ½ + isomer peak

Other yttrium transitions? 311nm J=0 → J=1 transition (2002) – 1 in efficiency

State selection in an ion cooler Ti:Sa

363 nm pumping of yttrium 1 photon for every 6000 ions becomes 1 for every 3000 ions (End of the beam line) Indifference to bunching Pumping saturates at 30mW Can use broadband lasers

98m 321.7nm predicted structure

Cerium Ti:Sa scan

Other pumping cases Zr, Nb, Mo, Rh, Ta, W... 2 photon M1/E2

Other possibilities: background suppression Broadband laser pumping step High resolution laser step High resolution laser step Decay detected by PMT

Future work: polarisation F=5/2 F=3/2 M F =-5/2 -3/2 -1/2 +1/2+3/2+5/2 -3/2 -1/2 +1/2+3/2 In a strong magnetic field, the spins decouple leaving the nuclear spins polarised and allowing NMR experiments to be performed Weak magnetic field ⇒ Zeeman splitting σ + circularly polarised light ⇒ spin polarisation in state of maximum M F

Summary Method of controlling state population Choose transitions on basis of strengths, spins, splitting and charge state Cooler provides a focal point of slowly travelling ions Ti:Sa lasers provides wider range of wavelengths and bandwidth or pulsing does not matter Necessary for yttrium; other cases being considered Aim to produce polarised beams out of the cooler for β -NMR work

Collaborators The University of Manchester, UK The University of Birmingham, UK The JYFL accelerator laboratory, Jyväskylä, Finland J. Billowes, P. Campbell, B.Cheal, B.A. Marsh, B.W. Tordoff T. Eronen, J. Huikari, A. Jokinen, T. Kessler, I.D. Moore, A. Niemenen H. Pentillä, S. Rinta-Antila, J. Äystö M.L. Bissell, D.H. Forest, G. Tungate