International Nuclear Physics Conference 2007 Jun 4 Hyperfine

International Nuclear Physics Conference 2007 - Jun. 4 - Hyperfine structure of 85, 87 Rb and 133 Cs atoms in superfluid helium Development of new laser spectroscopy project using superfluid helium stopper Takeshi Furukawa Nishina-Center, RIKEN Collaborator Y. Matsuo 1, A. Hatakeyama 2, T. Ito 3, K. Fujikake 3 T. Kobayashi 1, and T. Shimoda 4 1 Nishina-Center, RIKEN, 2 Dept. Appl. Phys. , Tokyo Univ. of Agr. Tech. , 3 Dept. Phys. , Meiji Univ. 4 Dept. Phys. , Osaka Univ.

International Nuclear Physics Conference 2007 - Jun. 4 - Contents 1) Our New laser spectroscopy project ・Double resonance method in He II Laser spectroscopy & optical detection Optical pumping in He II ( 2) Measurement data in the development ・Long atomic spin relaxation time in He II ・hyperfine resonance spectrum of 85, 87 Rb and 133 Cs in He II ・determination of nuclear magnetic dipole moment ・hyperfine anomaly in He II 3) Summary and future prospect

International Nuclear Physics Conference 2007 - Jun. 4 - Overview of Our Method Development : laser spectroscopy for short-lived RI atoms OROCHI project (tentative) Optical RI-atom Observation in Condensed Helium He II liquid RI atom purpose Systematical measurement of unknown hyperfine structures in exotic RI atoms Laser RI beam Laser induced fluorescence (LIF) effective stopping & trapping of RI atoms wavelength separator & photon detector using superfluid helium as a stopper & trap from “DRAEMON” vol. 22, by FUJIKO, F. Fujio

International Nuclear Physics Conference 2007 - Jun. 4 - Nuclear Laser Spectroscopy Contaminated atoms: no absorbing laser light → observe only objective atoms !! Laser induced fluorescence (LIF) photon He II absorb & emit photons cyclically → detect much photons/atom Laser (typically ~ 105 -108 photons /sec) → good statistic !! Scattered laser photon absorption spectra in He II : largely broadened & blue-shifted. RI beam wavelength : λatoms ≠ λ laser suppress the detection of scattered laser light feasible to achieve optical pumping of various atomic species i. e. ) In, Tl, ….

International Nuclear Physics Conference 2007 - Jun. 4 - Double Resonance Method Purpose: measure the hyperfine structure of RI atom LIF intensity expected spectrum microwave frequency Polarized atoms : Can not absorb circularly polarized laser light. LIF Intensity ∝ 1 - Pz

International Nuclear Physics Conference 2007 - Jun. 4 - Spin relaxation in He II To polarize the atoms : spin relaxation time is important long spin relaxation time in He II has been measured. feasible to achieve optical pumping 133 Cs atoms in He II extremely longer than optical pumping time T. Furukawa et al. , Phys. Rev. Lett. 96, 095301 (2006)

International Nuclear Physics Conference 2007 - Jun. 4 - Experimental Setup Measurement of the hyperfine splitting in Cs, Rb atoms Cs. I Cs Cs

International Nuclear Physics Conference 2007 - Jun. 4 - Double resonance peak in He II Hyperfine resonance measurement ：stable 133 Cs, 85, 87 Rb measured spectrum using double resonance method ν 133 Cs= 9. 2580915 (4) GHz ν 85 Rb= 3. 05802 (10) GHz A 85 Rb = 1. 01702(2) GHz A 133 Cs = 2. 312 76(2) GHz （Preliminary） ν 87 Rb= 6. 87652 (10) GHz A 87 Rb = 3. 43517(4) GHz （Preliminary）

International Nuclear Physics Conference 2007 - Jun. 4 - Hyperfine Structure in He II Pressurized by helium Hyperfine coupling constant A He II (GHz) DA/A (%) H (> H) H’ 2. 31276 (2) 2. 2981579 0. 635 (1) 133 Cs Rb Vacuum (GHz) 85 1. 01702 (2) 1. 0119109 0. 505 (2) 87 3. 43517 (4) 3. 4173413 0. 522 (1) Calcuration from hyperfine coupling constant m. I 85 Rb (m. N) 85 D 87 This work (from AHe. II) 1. 357 84 (1) m. N 0. 331 7 (7) % literature value 1. 353 351 5 m. N 0. 348 7 (3)% difference 0. 331 7 (7) % 4. 8 (2) % In He II electron nuclei Enable to obtain the nuclear information efficiently!!

International Nuclear Physics Conference 2007 - Jun. 4 - for RI Beam Experiment to confirm the feasibility of our project measure the LIF photons from RI atoms Wavelength plate Laser Induced Fluorescence 　　（LIF） Lens Optical filter Lens estimated lower limit of the beam intensity to measure：only 10 cps

International Nuclear Physics Conference 2007 - Jun. 4 - Conclusion We are now developing successfully… OROCHI project (tentative) Optical RI-atom Observation in Condensed Helium measure the hyperfine structure of exotic RI atoms 133 Cs, 85, 87 Rb hyperfine splitting in He II ・deduce nuclear moment with 1% accuracy ・deduce hyperfine anomaly with 5% accuracy * Nuclear spin can be also determined with rf-resonance ~Next plan~ + RI beam experiment (plan: in next year) + Optical pumping of various elements (In, Tl, Ca, …. ) Goal : measurement of In, Tl isotopes

International Nuclear Physics Conference 2007 - Jun. 4 - ふろく Additional OHP

Pressure effect in He. II Hyperfine coupling constant He. II (GHz) vacuum (GHz) He. II/vacuum ratio 2. 31276(2) 2. 29815794 1. 00635(1) 85 1. 01702(2) 1. 01191092 1. 00505(2) 87 3. 43517(4) 3. 41734131 1. 00522(1) 133 Cs Rb A=m. I<H>/I・J Difference of <H> in He II Compressed atom by surrounding helium Affect to the orbital of valence eveltrons VCs＞VRb ＜ 1% increase ΔCs＞ΔRb Pressurized by helium H’H(> H)

Determination of 85 Rb moment Deduce 85 Rb moment with 87 Rb moment as reference Use A value in vacuum: literature value： ・possible to determine the moment with 1% accuracy ・difference (～ 0. 3%) ← caused by hyperfine anomaly electron nuclei Effect of the distribution of nuclear magnetization

Hyperfine anomaly in He II Considering hyperfine anomaly… In He. II In vacuum ) hyperfine anomaly ～５％ difference In vacuum Due to the deformed electron distribution by the pressure of surrounding He ? ? In He. II

Hyperfine Interaction W(F, m. F)= A・K/2 + B・{3 K(K+1)/4 –I(I+1)J(J+1)}/{2(2 I-1)(2 J-1)IJ} [K=F(F+1)-I(I+1)-J(J+1)] A=m<B>/IJ B=e. Q<V> I: nuclear spin, J: electronic angular momentum, m: nuclear magnetic dipole moment, e. Q: 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 m. X and n. X mm. X Am. X Im. X mn. X = A I n. X e. Qm. X Bm. X = e. Qn. X Bn. X

Effect of surrounding He atoms ① Blue-Shifted absorption spectrum in He II ② Broadened ( Bubble model absorption Energy Deform absorption emission Deform Bubble radius Energy levels in the ground state and excited state as a function of bubble radius.

Excitation Spectrum in He II ① Blue-Shifted absorption spectrum in He II ② Broadened ( by the pressure of surrounding He atoms atomic spectra in He II Intensity (arb. unit) 133 Cs emission：peak ~892 nm, width ~3 nm (in vacuum: 894. 347 nm) absorption：peak ~876 nm, width ~15 nm absorption≠emission Wavelength (nm)

Optical Merit in He II ① Blue-Shifted absorption spectrum in He II ② Broadened ( In vacuum In He II Laser Need many laser lights! Detector Excitation with only single laser light wavelength: l. LIF ≠ llaser suppress the detection of scattered laser light Feasible to acheve optical pumping

Optical Pumping Optical pumping method （in the case of alkali atoms J=1/2） atom laser B P 1/2 σ+ D 1 Line S 1/2 σ+ X After the polarizing of atoms… Decrease LIF intensity (Laser Induced Fluorescence, LIF) m = -1/2 m = +1/2 LIF Intensity ∝ 1 - Pz

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

Relaxation in the Dark Method Measure the relaxation time →“Relaxation in the dark” method detect the photons only from the “spin relaxed” atoms

Timing chart

Spin relaxation time in He II Dark period後のLIF強度 偏極ゼロ時のLIF強度

Measured LIF intensity

Demerits in Optical Detection Problems in laser spectroscopic study of RI atoms ・stopping & Trapping efficiency ・possible elements B. G. count of stray light In He II・・・ Introduced to condenced helium → observe all of the stopped atoms high trapping efficiency Laser RI Beam Stopped & trapped Using the characteristic spectrum of atoms in He II →Subtract the problems Interaction with surrounding He

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

Scientific Motivation 目標：短寿命不安定核の系統的核モーメント測定法開発 Nuclear moments Nuclear structure however… Unstale nuclei near the drip-line ・low yield ・low purity ・small polarization Difficult to measure!! ex) b-NMR method detector Polarized RI nucleus stopper detector Signals from RI そこで… 『Laser spectroscopy of stopped RI atoms in He. II』 に着目