Laser-microwave double resonance method in superfluid helium for the measurement of nuclear moments Takeshi Furukawa Department of Physics, Graduate School of Science, Osaka University Collaborator Y. Matsuo 2, A. Hatakeyama 3, T. Ito 4, Y. Ota 4, Y.Fukuyama 2, T. Kobayashi 2, and T. Shimoda 1 1 Dept. Phys., Osaka Univ., 2 RIKEN, 3 Inst. Phys., Univ. of Tokyo, 4 Dept. Phys., Meiji Univ.

1) Problems in measuring the nuclear moment 2) Double resonance method to cope with the problems Contents 3) Present status of the development 4) Summary and future prospect ・ Low-yield, high-contamination, small-polarization of unstable nuclei Laser spectroscopy & optical detection ・ Double resonance method in He II Optical pumping in He II ( ・ Long atomic spin relaxation time in He II ・ Hyperfine transition spectrum in He II

Scientific Motivation Unstable nuclei near the drip-line Polarized RI nucleus detector stopper Signals from RI detector ex  -NMR method ・ low-yield ・ high-contamination ・ small-polarization Difficult to measure the nuclear moment ) Laser spectroscopy & optical detection of RI atoms Optical pumping in He II Measure the hyperfine structure Determination of nuclear moments

Merit in Optical Detection Pumping the RI atoms repeatedly. Detecting the LIF photons repeatedly. The impurity atoms can not absorb the pumping laser. Insensitive detection to the impurity atoms. Laser RI beam low yield, high contamination Laser spectroscopic method is suitable for unstable nuclei. Laser Induced Fluorescence (LIF) photon Good S/N ratio Useful to measure the unstable nuclei

We plan to measure the h.f.s with the double resonance method. LIF Intensity ∝ 1 - P z Double resonance method Polarized atoms : Can not absorb circularly polarized laser light. Measure the constant A, B of isotope m X and n X  mX  nX = A mX I mX A nX I nX eQ mX eQ nX B mX B nX = Hyperfine Structure (J=1, I=3/2 case) A=  /IJ B=eQ I:nuclear spin, J:electronic angular momentum,  : nuclear magnetic dipole moment, eQ: nuclear electric quadrupole moment, :magnetic field produced by the electrons :electric field gradient produced by the electros J=1, I=3/2 F=5/2 F=3/2 F=1/2 5/2A 3/2A 5/2A+5/4B 3/2A-9/4B LIF intensity microwave frequency expected spectrum Limited to alkali-like atoms Optical pumping is performed only alkali-like atoms.

Optical pumping in He II In vacuumIn He II Many lasers needed. Only one laser beam induce to polarization. Optical spectrum of atoms is dynamically broadened due to the influence of the surrounding He atoms. Mg 3s3p 3 P 2,1,0 3s4s 3 S 1 Transition In He II: possible to polarize various atoms with optical pumping Possible to optically pump the atoms with complicated level structure using a single laser beam Problem: How fast spin relaxes in He II ?

Spin polarization in He II Long spin relaxation time are expected in He II ! Low temperature Small polarizability Spin-less atom How long the relaxation time ? We have measured T 1 of Cs atoms in He II Spin relaxation of Cs atoms relaxing time Achieved polarization : ~90 % in Cs Relative polarization Optical pumping of the atoms other than alkalis is now in progress. T. Furukawa et al., submitted to Phys. Rev. Lett. He II is suitable to use with our method.

Hyperfine structure of 133 Cs Hyperfine structure of 133 Cs atom F=4 F=3 m F =+4~-4 9 levels m F =-3~+3 7 levels 6s 2 S 1/2 Hyperfine splitting energy E h.f.s = A ・ F = 4A (A ∝ μ I ) Double Resonance spectrum of Cs atoms in He II Check the feasibility in He II With σ + pumping With σ - pumping m F = F=4 F=3 m F = ν+ν+ ν-ν- ν 0 = (ν + + ν - ) /2 Details of 133Cs hyperfine transition

Measurement Result of Hyperfine Splitting ν σ+ = (9) GHz ν σ- = (4) GHz ν 0 = (ν σ+ + ν σ- )/2 = (98) GHz ∴ A = ν 0 / F = (25) ( in vacuum: GHz ) ~0.65% larger !!! Preliminarily result

Pressure effect in He II H A = ν0 / F = (25) ( in vacuum: GHz ) ~0.65% larger !!! A=   /IJ Large in He II Because of compressed electron orbit pressurized with surrounding He atoms H ’ (> H) Pressurized by helium No difference in isotopes ?? Next plan : Check the difference of between 85,87 Rb

Summary and Future prospect Double Resonance in He II Measurement Method for the nuclei near the drip-line Meri t ・ Detecting the LIF photons repeatedly ・ Insensitive to the impurity atoms ・ Long spin preservation, high polarization Future prospect Optical detection from low-yield RI atoms Optical pumping of various atoms other than alkalis (Mg, Al,..) Measure the moments of various nuclei ( 22 Al, 21 Mg,...) Problems ・ low-yield ・ high-contamination ・ small-polarization ・ High polarization, long spin reservation, and precise resonance spectrum are confirmed in He II

Additional OHP

Hyperfine Interaction W(F, m F )= A ・ K/2 + B ・ {3K(K+1)/4 – I(I+1)J(J+1)}/{2(2I-1)(2J-1)IJ} [K=F(F+1)-I(I+1)-J(J+1)] Measure the constant A, B of isotope m X and n X A=  /IJ B=eQ I:nuclear spin, J:electronic angular momentum,  : nuclear magnetic dipole moment, eQ: nuclear electric quadrupole moment, :magnetic field produced by the electrons :electric field gradient produced by the electros  mX  nX = A mX I mX A nX I nX eQ mX eQ nX B mX B nX =

Timing Chart of Measurement Pumping laser polarization linearly circularly linearly Counting gate Count1Count2Count3 LIF Intensity With microwave resonance ∝ N Cs ∝ N Cs (1-P laser P atom ) LIF ratio : P atom → small (with M.R.) Ratio → Large

Experimental Setup

Atomic level energy W = W J + A ・ K/2 + W B + g F μ B Bm F In 133 Cs case ( |F, mf ＞ : |4, +4 ＞ → |3, +3 ＞ )…. ΔW σ+ = W(4, +4) - W(3, +3) = A ・ F + g J μ B B×7/8 ΔW σ- = W(4, -4) - W(3, -3) = A ・ F - g J μ B B×7/8 K = F(F+1) - I(I+1) - J(J+1) Hyperfine Splitting of 133 Cs

Timing Chart LIF ratio : Count2 / { (Count1 + Count3) /2 }

Double Resonance Method Need more effective measurement method! Laser Double Resonance Method in He II is suitable for the measurement. Laser Induced Fluorescence （ LIF ） Len ｓ Lens Optical filter Double resonance method a sort of laser spectroscopy

Bubble Model Atoms in He II: repel the surrounding helium atoms (by Pauli repulsion) Deform absorb the photonemit the photon Energy Like as bubble absorption emission Bubble radius Energy levels in the ground state and excited state as a function of bubble radius.

Physics motivation 22 Al : proton halo? 21 Mg : Isospin symmetry? 22 Al = 21 Mg + p 21 Mg- 21 F mirror pair in T = 3/2 35 Ca : Z=20 magic?

Optical Pumping of Metastable Mg atoms 21 Mg atomic energy diagram Observable resonance line (Assume I = 5/2) 3s3p 3 P 2 F=9/2 ⇔ F=7/2 [h.f.s = (9/2)A + (27/40)B] F=7/2 ⇔ F=5/2 [h.f.s = (7/2)A + (7/40) B] ( 3s3p 3 P 1 F=7/2 ⇔ F=5/2 )

Relaxation in the Dark Method

Timing chart

Measured LIF intensity

Spin Relaxation Mechanism

M.R. Spectrum in He II Peak frequency:959.5(5) kHz Double Resonance spectrum of Cs atoms in He II (Zeeman sublevel transition, Magnetic field : ~ 3 G) Energy level of g.s Cs atom... F=4 F=3 6s 1/2 Zeeman transition Hyperfine transition Observing hyperfine resonance same as that Nuclear moments can be determined precisely Check the feasibility in He II (preliminary)