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Laser spectroscopy of radioactive atoms embedded in superfluid He ,

International Workshop on Physics of Nuclei at Extremes, ‘10 1/26 Tokyo TECH. Laser spectroscopy of radioactive atoms embedded in superfluid He , and a planned nuclear structure study on proton-rich Ag isotopes - “OROCHI” project -. Tokyo Institute of Technology. Takeshi Furukawa.

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Laser spectroscopy of radioactive atoms embedded in superfluid He ,

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  1. International Workshop on Physics of Nuclei at Extremes, ‘10 1/26 Tokyo TECH Laser spectroscopy of radioactive atoms embedded in superfluid He, and a planned nuclear structure study on proton-rich Ag isotopes -“OROCHI” project - Tokyo Institute of Technology Takeshi Furukawa

  2. Contents ・What is “OROCHI” ? nuclear laser spectroscopy in superfluid helium for the measurement of rare isotopes not with high precision , but with sensitive to detect photons ・Present status of “OROCHI” off-line development with Rb, Cs, Ag, and Au stable isotopes ・Future prospect of “OROCHI” on-line experiment plan for proton-rich Ag isotopes IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa

  3. Zeeman splittings hyperfine structures F e external magnetic field B J I hyperfine interactions interaction between nuclear moments and electrons interaction between atomic spin mF and external magnetic field atomic sublevel structure I J Introduction: Measurement of Nuclear Spin and Moment Nuclear structure Laser spectroscopy nuclear spins one of the most important quantities for nuclear structure investigation ex) orbital angular momentum of valence nucleons, configuration mixing ….. electromagnetic moments However... Nuclear spin/moment measurement on unstable nuclei far from stability line : difficult - low yield - large contamination - small polarization IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa

  4. “OROCHI” Optical Radioisotope-atom Observation in Condensed Helium as Ion-catcher He II Laser from “DRAEMON” vol. 22, by FUJIKO, F. Fujio New Laser Spectroscopy to measure the nuclear spins & moments in exotic nuclei… “laser spectroscopy for radioisotope atoms in superfluid helium (He II)” RI beam Ion beam (radioisotope beam) target Accelerator (i.e. SRC in RIKEN) Separator (i.e. BigRIPS in RIKEN) hyperfine structure Zeeman structure (((((( nuclear moment nuclear spin radiowave or microwave LIF IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa

  5. Advantage in HeII We use He II to reduce the b.g. photons. ① blue-shifted ( Atomic absorption spectra in He II ② broadened 133Cs atomic spectra in He II in vacuum Excited with expanding the surrounding He atom Laser emission Intensity (arb.unit) He II absorption Detector He II wavelength:lLIF≠llaser 光波長 (nm) Wavelength (nm) Suppress background count Reduction:10-10～10-13 IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa

  6. Contaminant atoms: do not absorb laser light →observe only objective atoms !! absorb & emit photons cyclically → detect much photons/atom (typically ~ 105-108 photons /sec) →good statistic !! Advantages of laser spectroscopy Laser induced fluorescence (LIF) photon Scattered laser photon Laser RI beam IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa

  7. expected spectrum P1/2 P1/2 P1/2 ILIF σ+ σ+ σ+ σ+ σ+ σ+ X X X D1 Line D1 Line S1/2 S1/2 S1/2 m = -1/2 m = -1/2 m = -1/2 m = +1/2 m = +1/2 m = +1/2 rf frequency Double resonance spectroscopy measurement of atomic sublevel structure ：Double resonance spectroscopy In the case of Zeeman splitting in alkali atoms 1st step : optical pumping 2nd step: double resonance m = +3/2 m = +3/2 m = +3/2 atoms laser No level B Emission photons in optical pumping (Laser Induced Fluorescence, LIF) rf-resonance (((((( (((((( decreased gradually [ILIF] ∝ 1 - Pz rf IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa

  8. Experimental Setup To confirm the feasibility of OROCHI with stable isotope: Rb, Cs, Ag, Au, …. IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa

  9. Polarization ：~90 %(Cs) ~50 %(Rb) Optical pumping in He II T. Furukawa et al., Phys. Rev. Lett. 96, 095301 (2006) Produce the polarization in stable Rb, Cs in He II Polarization switched Polarization: increased LIF intensity: decreased (Laser induced fluorescence) Linearly polarized Circularly polarized IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa

  10. Spin preservation in He II - spin relaxation time of 133Cs atoms in He II - long relaxation time (Cs atomic spin) T. Furukawa et al., Phys. Rev. Lett. 96, 095301 (2006) In He II : atoms can be polarized easily IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa

  11. Zeeman splittings mI85Rb (mN) 1.357 83 (7) mN This work (from AHeII) 1.358 071(1) mN evaluated (from Avacuum) 1.353 351 5 mN literature value (NMR) Nuclear spin & moment determination atomic sublevel structure hyperfine splitting Zeeman resonance of Rb isotopes Hyperfine resonance of 85Rb I85Rb = 2.6(1) → 5/2 I87Rb = 1.55(5) → 3/2 ΔnZmn = gF mB B / h 2.8(MHz)×B(Gauss) = (2I+1) Nuclear spin T. Furukawa, Doctoral thesis, Osaka Univ. (2007) IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa T. Furukawa, et.al., Proceedins on INPC07 (2008)

  12. Hyperfine coupling constant A HeII/vacuum ratio HeII (GHz) vacuum (GHz) 133Cs 1.00638(1) 2.31283(3) 2.29815794 B 85 1.00503(3) 1.01191092 1.01700(3) Rb 87 1.00521(1) 3.43514(5) 3.41734131 Pressurized by helium <B> isotope： same atomic structure →approximately same <B> w/o hyperfine anomaly (Bohr-Weisskopf effect) B’ (> B) Hyperfine structure in He II - Atomic hyperfine structure in He II - T. Furukawa et al., to be submitted... In He II density hyperfine anomaly In vacuum density radius electron cloud nucleus radius IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa

  13. Our achievement Off-line development with stable isotope ・determine nuclear spin & moment : Cs, Rb isotopes ・Producing high polarization in alkali Cs, Rb atoms Can we apply this OROCHI to atoms other than alkali? Recently… applying OROCHI to noble metal Ag, Au atoms. IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa

  14. D1excitation spectrum of Ag atoms in HeⅡ 107,109 Ag, width：～5nm Ag atom: peak ：～333.5nm 2 S 2 P 1/2 1/2 Optical pumping of Ag, Au atoms I=1/2 mF F=0 0 Ag, Au： atomic level structure is same as alkalis. +1 F=1 0 Feasible to optical pumping. However…. (in free-space) -1 338.29nm F=0 0 No strong laser source just suited to absorption line Absorption line : in UV region +1 F=1 0 -1 In the case of He II… Broadened absorption spectra. We can prepare the pumping laser. IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa

  15. Ag atomic sublevel structure I J Laser spectroscopy of Ag and Au T. Furukawa, K.Fujikake et al., to be published... Applying to noble metal Ag and Au atoms Broadened absorption spectra in He II. → feasible to optical pumping of various atomic species (less limitation in laser wavelength) polarization：～８０％(Ag), ～６０％(Au) incomplete polarization is due to imperfect circular polarization of laser Zeeman splitting of stable 107,109Ag isotopes (both I=1/2 ) Preliminary ) ΔEZMN Nuclear spin I=1/2 can be deduced clearly. IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa

  16. Our achievement Off-line development with stable isotope ・determine nuclear spin & moment : Cs, Rb isotopes ・applying to Ag and Au atoms : successful Can we apply this OROCHI to atoms other than alkali? ・Producing high polarization in alkali Cs, Rb atoms next step: On-line experiment IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa

  17. N Stable line N＝５０ Z Z＝５０ N＝８２ g.s. moment is unknown Stable isotope g.s. moment is known g.s. moment is zero (even-even nuclei) N. J. Stone, At. Nucl. Data Tab. 90, 75 (2005) Future prospect RI (total): 0.1 pps Isomer ratio: 5 % (from RIBF facility) 1 day measurement measurable 1st goal :exotic N=Z nucleus 94Ag I, m of g.s. and isomer state (21+) expected yield: < 1 pps (with BigRIPS) simulation IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa

  18. On-line experiment with Rb beam - 1st trial - All the devices were mounted on RIKEN RIPS beam line!! cryostat But Rb beam has not accelerated due to machine trouble… Oh, my god...... laser Rb beam Cryostat Rb beam The result will be shown next time … Photo-detection system IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa

  19. “OROCHI”Project Optical Radioisotope-atom Observation in Condensed Helium as Ion-catcher Conclusion • We developed the new laser spectroscopy method “OROCHI” for determining • nuclear spins and moments of exotic RI far from stability by using superfluid • helium (He II) as a stopper of RI beam and host matrix of laser spectroscopy. • Atomic spectra in He II (largely blue-shifted and broadened) enable us • to measure for the extremely low yield RI whose yield is less than 1 pps. • In our off-line development using stable Rb and Cs isotopes, we have • successfully demonstrated the determination of nuclear spins and moments • from the measured Zeeman and hyperfine splitting respectively. • We have also demonstrated the optical pumping and double resonance • of stable Ag and Au isotopes in recently. • Preparation of setups for online experiment is almost finished. We hope This OROCHI will open the door to measure the nuclear spins and moments of exotic nuclei, particularly proton drip-line, N=Z nucleus 94Ag IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa

  20. OROCHI - Collaborator Spokesperson: Takeshi Furukawa (Tokyo Institute of Techinology), Yukari Matsuo (RIKEN) Email: takeshi@yap.nucl.ap.titech.ac.jp RIKEN： H. Ueno, N. Aoi,A. Yoshimi, K. Yoneda, Y. Togano, M. Takechi, Y. Ichikawa, S. Nishimura, M, Nishimura, T. Kobayashi, M. Wada, T. Sonoda, A. Takamine, T. Motobayashi, … Tokyo institute of Technology: K. Asahi, Y. Kondo CYRIC, Tohoku Univ.: A. Sasaki, T. Wakui, H. Oouchi, S. Izumi, T. Shinozuka Osaka Univ.: M. Kazato, T. Shimoda, A. Odahara • This project is supported by • - Grant-in-Aid for Scientific Research • by the Ministry of Education, Culture, • Sports, Science, and Technology, Japan. • Program for Global Center of Excellence • “Nano-science and Quantum Physics” • in Tokyo Institute of Technology Tokyo Univ. of Agriculture and Tech.： A. Hatakeyama Meiji Univ.: Y. Matsuura, H. Kato CNS, Univ. Tokyo: S. Kubono, Y. Oshiro

  21. Thank you for your attention. IWPNE 2010, 2010 1/26 Tokyo TECH, T. Furukawa

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