Takeshi Furukawa

Laser-microwave double resonance methodin superfluid heliumfor the measurement of nuclear moments Takeshi Furukawa Department of Physics, Graduate School of Science, Osaka University Collaborator Y. Matsuo2, A. Hatakeyama3, T. Ito4, Y. Ota4, Y.Fukuyama2, T. Kobayashi2, and T. Shimoda1 1Dept. Phys., Osaka Univ., 2RIKEN, 3Inst. Phys., Univ. of Tokyo, 4Dept. Phys., Meiji Univ.

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

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

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

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

In vacuum In He II Only one laser beam induce to polarization. Many lasers needed. Optical pumping in He II In He II: possible to polarize various atoms with optical pumping Optical spectrum of atoms is dynamically broadened due to the influence of the surrounding He atoms. Possible to optically pump the atoms with complicated level structure using a single laser beam Mg 3s3p 3P2,1,0 3s4s 3S1 Transition Problem: How fast spin relaxes in He II ?

Spin polarization in He II Long spin relaxation time are expected in He II ! How long the relaxation time ? Low temperature Small polarizability We have measured T1of Cs atoms in He II Spin-less atom Spin relaxation of Cs atoms Achieved polarization : ~90 % in Cs He II is suitable to use with our method. Relative polarization Optical pumping of the atoms other than alkalis is now in progress. T. Furukawa et al., submitted to Phys. Rev. Lett. relaxing time

mF=+4 Details of 133Cs hyperfine transition +3 +2 +1 0 F=4 -1 -2 With σ+ pumping -3 -4 ν+ With σ- pumping ν- ν0= (ν+ + ν-) /2 -3 -2 -1 F=3 0 +1 +2 mF=+3 Hyperfine structure of 133Cs Check the feasibility in He II Double Resonance spectrum of Cs atoms in He II Hyperfine structure of 133Cs atom mF=+4~-4 9 levels F=4 Hyperfine splitting energy Eh.f.s = A・F = 4A (A ∝ μI) 6s 2S1/2 mF=-3~+3 7 levels F=3

Measurement Result of Hyperfine Splitting Preliminarily result νσ+=9.257705(9) GHz νσ-=9.243484(4) GHz ν0 = (νσ+ + νσ-)/2 = 9.2505945(98) GHz ∴ A = ν0 / F = 2.3126486(25) ~0.65% larger !!! ( in vacuum: 2.298157943 GHz )

Pressurized by helium H H’ (> H) Pressure effect in He II A = ν0 / F = 2.3126486(25) ~0.65% larger !!! ( in vacuum: 2.298157943 GHz ) A=mI<H>/IJ Large <H> in He II Because of compressed electron orbitpressurized with surrounding He atoms No difference in isotopes ?? Next plan : Check the difference of <H’> between 85,87Rb

Summary and Future prospect Measurement Method for the nuclei near the drip-line Double Resonance in He II Problems Merit ・low-yield ・Detecting the LIF photons repeatedly ・high-contamination ・Insensitive to the impurity atoms ・small-polarization ・Long spin preservation, high polarization ・High polarization, long spin reservation, and precise resonance spectrum are confirmed in He II 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 (22Al, 21Mg,...)

Additional OHP

Hyperfine Interaction Hyperfine Interaction W(F, mF)= 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)] A=m<B>/IJ B=eQ<V> I:nuclear spin, J:electronic angular momentum, m: nuclear magnetic dipole moment, eQ: nuclear electric quadrupole moment, <B>:magnetic field produced by the electrons <V>:electric field gradient produced by the electros Measure the constant A, B of isotope mX and nX mmX eQmX AmX ImX BmX = = mnX AnX InX eQnX BnX

With microwave resonance Timing Chart of Measurement linearly linearly Pumping laser polarization circularly Counting gate Count1 Count2 Count3 ∝NCs ∝NCs(1-PlaserPatom) ∝NCs LIF Intensity Patom→small (with M.R.) LIF ratio : Ratio→Large

Experimental Setup

Hyperfine Splitting of 133Cs Atomic level energy W = WJ + A・K/2 + WB + gFμBBmF K = F(F+1) - I(I+1) - J(J+1) In 133Cs case ( |F, mf ＞: |4, +4＞ → |3, +3＞)…. ΔWσ+ = W(4, +4) - W(3, +3) = A・F + gJμBB×7/8 ΔWσ- = W(4, -4) - W(3, -3) = A・F - gJμBB×7/8

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. Double resonance method a sort of laser spectroscopy Lenｓ Laser Induced Fluorescence 　　（LIF） Optical filter Lens

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

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

Optical Pumping of Metastable Mg atoms 21 Mg atomic energy diagram Observable resonance line (Assume I = 5/2 ) 3 3s3p P F=9/2 ⇔ F=7/2 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] 3 ( 3s3p P F=7/2 ⇔ F=5/2 ) 1

Relaxation in the Dark Method

Timing chart

Measured LIF intensity

Spin Relaxation Mechanism

M.R. Spectrum in He II Check the feasibility in He II Energy level of g.s Cs atom Double Resonance spectrum of Cs atoms in He II Zeeman transition (Zeeman sublevel transition, Magnetic field : ~ 3 G) F=4 ... 6s1/2 Hyperfine transition F=3 Peak frequency:959.5(5) kHz (preliminary) Observing hyperfine resonance same as that Nuclear moments can be determined precisely

Takeshi Furukawa