1. He II (2) Atomic photon spectroscopy in condensed helium The 4th Yamada Symposium on Advanced Photons and Science Evolution 2010 APSE 2010 2010.06.14 RIKEN Nishina Center for Accelerator-Based Science Yukari Matsuo Advanced atomic photon spectroscopy (1) Advanced atomic photon spectroscopy atoms laser photon RI Beam (3) Application to precision laser spectroscopy of atoms with unstable nuclei

2. 2010.06.14 APSE2010 Outline (1) Advanced atomic photon spectroscopy - Atomic laser spectroscopy - High precision spectroscopy for fundamental physics … nuclear physics (2) Atomic photon spectroscopy in condensed helium - Characteristic of atoms in superfluid helium (He II) - Precision laser spectroscopy of atoms in He II (3) Application of precision laser spectroscopy to atoms with unstable nuclei - Novel nuclear laser spectroscopy of RI atoms in He II : OROCHI (4) Summary

3. 2010.06.14 APSE2010 Atomic spectroscopy 19th. Century Fraunhofer lines in the optical spectrum of the Sun Optical atomic spectra reflect structure of atoms and nuclei. (Å)(Å) energy level Balmer series Lyman series Hydrogen emission lines absorption emission atom Discrete lines could not be explained without quantum theory

4. 2010.06.14 APSE2010 Laser spectroscopy conventional laser spectroscopic methods easily reach to an accuracy of 10 -8 – 10 -9 Development of laser has dramatically improved measurement techniques Before lasers diffraction gratings played leading roles. slit spectrum of sample light source spectrum The information is limited by the resolution of light source laser light light source spectrum spectrum of sample Narrow band of laser light sources enables measurement with higher resolution, because transition frequency of isolated atoms is narrow. For higher resolution, spectral widths of sample need to be reduced…

5. 2010.06.14 APSE2010 For the higher accuracy It is necessary to reduce the factors to determine linewidth and uncertainty Doppler widthCollisional widthNatural width Frequency uncertainty … Optical frequency comb T. Rosenband, et al., Science 319, 1808 (2008) ~ 10 -19 F. Hong, et al., APEX 2, 072501 (2009) 171 Yb Forbidden transition High vacuum Doppler cooling ~  K BEC ~ nK Trap / Cooling

6. 2010.06.14 APSE2010 State-of-the-art experiment

7. 2010.06.14 APSE2010 State-of-the-art experiment

8. 2010.06.14 APSE2010 For the higher accuracy It is necessary to reduce the factors to determine linewidth and uncertainty Doppler widthCollisional widthNatural width Frequency uncertainty … Optical frequency comb T. Rosenband, et al., Science 319, 1808 (2008) F. Hong, et al., APEX 2, 072501 (2009) 171 Yb ~ 10 -19 Forbidden transition High vacuum Doppler cooling ~  K BEC ~ nK Trap / Cooling Discussion on temporal variation of fine structure constant  Frequency standard

9. 2010.06.14 APSE2010 Atomic laser spectroscopy and the study of nuclei Laser light emission atom alkaline –like atoms D P S Orbital angular momentum ＝ 2 ＝ 1 ＝ 0 Fine-structure e.g. splitting of D line in Na atom L+S=J S L s=½s=½ L ≧ 1 levels split due to spin-orbit interaction (LS-coupling) 2 D 5/2 2 D 3/2 2 P 3/2 2 P 1/2 2 S 1/2 D1D1 D2D2 Precision measurement of atomic sublevel structures can provide valuable information on nuclear structure because nuclear spins and moments are fundamental physical quantities of nuclei magnetic field Zeeman splitting Hyperfine structure J I nuclear spin Nuclear spins Nuclear moments Nuclear laser spectroscopy HFS for unstable 7 Be + is measured A = 742.772 28(43) MHz by RIKEN SLOWRI group K. Okada, et.al.,PRL 101, 212502 (2008)

10. 2010.06.14 APSE2010 Advanced atomic photon spectroscopy Brief summary and so forth … Nuclear structure study Atomic clock Frequency standard CPT violation? Search for EDM ⇒ The ultimate precision spectroscopic measurements can be regarded as a powerful tool to approach the fundamental physics and cosmology, including particle and nuclear physics Temporal variation of fine structure constant 

11. 2010.06.14 APSE2010 Outline (1) Advanced atomic photon spectroscopy - Atomic laser spectroscopy - High precision spectroscopy for fundamental physics … nuclear physics (2) Atomic photon spectroscopy in condensed helium - Characteristic of atoms in superfluid helium (He II) - Precision laser spectroscopy of atoms in He II (3) Application of precision laser spectroscopy to atoms with unstable nuclei - Novel nuclear laser spectroscopy of RI atoms in He II : OROCHI (4) Summary

12. Low temperature, trapping capability of He II would be a good environment for spectroscopy Large collisional broadening by surrounding He atoms will be an obstacle for precision spectroscopy What is the behavior of atoms in superfulid helium ?

13. 2010.06.14 APSE2010 Impurities in superfluid helium Electron bubble Snowball Atomic bubble Optical transition spectrum is observed in 1990 Laser spectroscopy started in 1980’s Optical emission is not observed Some ions behave like atomic bubble; Ba +, Yb +,... We will be focused on the bubble case ~17 Å ~several Å 1s-1p transition; 5~7  m 1s 1p 2p UV ~ visible ~ NIR region e-e- liquid helium bubble atom liquid helium bubble ion + liquid helium solid helium

14. 2010.06.14 APSE2010 Optical spectra (atomic-bubble model) ＋ e-e- He II absorption deform broad, large blue-shift absorptionemissionrelaxation sharp, small shift simple model describes spectra well bubble radius energy

15. 2010.06.14 APSE2010 Typical LIF spectra of atoms/ions in He II wavelength (nm) Intensity (arb.unit) absorption (broad) line position in vacuum emission (sharp) 133 Cs in He II 2 P 3/2 2 P 1/2 2 S 1/2 D1 894nm Cs D1 spectrum energy level in vacuum Kyoto group Takahashi, et.al., 1993 Ba + D1 spectrum Heidelberg group Reyher, et.al., 1986 energy level in vacuum 2 D 5/2 2 D 3/2 2 P 3/2 2 P 1/2 2 S 1/2 D1 493nm 650nm line position in vacuum absorption (broad) emission 650nm 493nm

16. 2010.06.14 APSE2010 Atoms and ions observed using laser spectroscopic method in He II atoms observed ions observed

17. 2010.06.14 APSE2010 Outline (1) Advanced atomic photon spectroscopy - Atomic laser spectroscopy - High precision spectroscopy for fundamental physics … nuclear physics (2) Atomic photon spectroscopy in condensed helium - Characteristic of atoms in superfluid helium (He II) - Precision laser spectroscopy of atoms in He II (3) Application of precision laser spectroscopy to atoms with unstable nuclei - Novel nuclear laser spectroscopy of RI atoms in He II : OROCHI (4) Summary

18. But, how one can do precision laser spectroscopy in superfluid helium? Combination of optical pumping & double resonance is a way out of the difficulty

19. 2010.06.14 APSE2010 Using superfluid helium as a matrix … HFS transition is observable using laser – microwave double resonance for Cs Takahashi, et.al. Z. Phys. B 98 (1995) 391 Multiple HFS levels can be optical pumped simultaneously Optical pumping with circular polarized light Laser  + M sub-levels population accumulated emission excitation potential energy r He-M broad, large blue-shift sharp, small shift S 0,0 P 1,0 large shift, broad spectrum could be an obstacle introducing atoms quietly was difficult...

20. 2010.06.14 APSE2010 Experimental setup our method introducing atoms/ions into He II above surface laser ablation method Femto sec pulsed Ti:S HeⅡHeⅡ He Ⅱ Superfluid fountain LIF Monochro -mator P.M.T Pumping laser EOM AOD sample Pulsed Nd:YAG atom cluster Helmholtz coil Ablation laser Dissociation laser He Ⅱ λ/4 Dipole antenna In 2000’s

21. 2010.06.14 APSE2010 Double resonance spectroscopy LIF decreases Double resonance spectroscopy MW RF m F = -1 F=1 0+1 0 F=0 2 S 1/2 2 P 1/2 m F = -1 F=1 0+1 0 F=0 X LIF intensity MW or RF frequency expected spectrum LIF increases Optical pumping m F = -1 F=1 0+1 0 F=0 2 S 1/2 2 P 1/2 m F = -1 F=1 0 +1 0 F=0 X m F = -1 F=1 0+1 0 F=0 2 S 1/2 2 P 1/2 m F = -1 F=1 0+1 0 F=0 X circularly polarized laser light Zeeman splittings hyperfine splitting atomic sublevel structures not much affected ground state excited state electronic transition is perturbed by surrounding He Mearsurement of atomic sublevel structures

22. 2010.06.14 APSE2010 Optical Pumping in He II Change the laser polarization linearly polarized light circularly polarized light Polarization ： ~90 %(Cs) ~50 %(Rb) Pumping time : ~1 ms (Cs & Rb) long spin relaxation time T. Furukawa et al., Phys. Rev. Lett. 96, 095301 (2006)

23. 2010.06.14 APSE2010 Zeeman splitting measurement atomic sublevel structure Zeeman splittings ΔE Zmn = g F  B B Zeeman splittings (alkali atoms, s-state) 2.8 (MHz) ×B (Gauss) = (2I+1) h ・ Zeeman splittings （ Rb isotope, 4 Gauss ） I 85Rb = 2.6(1) → 5/2 I 87Rb = 1.55(5) → 3/2 nuclear spins T. Furukawa, Doctoral thesis, Osaka Univ. (2007) T. Furukawa, et. al., Hyp. Int., 196, 191 (2010).

24. 2010.06.14 APSE2010 Hyperfine splitting measurement atomic sublevel structure Zeeman splittings hyperfine splitting hyperfine resonance: width-50kHz Precision measurement of hyperfine structure 同位体： 電子構造が同じ → が同じ magnetic moment This work (from A HeII ) evaluated (from A vacuum ) literature value  I 85Rb (  N ) 1.357 83 (7)  N 1.358 071(1)  N 1.353 351 5  N T. Furukawa, Doctoral thesis, Osaka Univ. (2007) T. Furukawa, et. al., Hyp. Int., 196, 191 (2010). ・ hyperfine structures （ Cs, Rb isotopes ） ・ as accurate as in vacuum ・ determine nuclear moments Electronic level structures are the same among isotopes → same

25. 2010.06.14 APSE2010 Hyperfine anomaly atomic sublevel structure Zeeman splittings hyperfine splitting hyperfine resonance: width-50kHz Precision measurement of hyperfine structure 同位体： 電子構造が同じ → が同じ magnetic moment This work (from A HeII ) evaluated (from A vacuum ) literature value  I 85Rb (  N ) 1.357 83 (7)  N 1.358 071(1)  N 1.353 351 5  N T. Furukawa, Doctoral thesis, Osaka Univ. (2007) T. Furukawa, et. al., Hyp. Int., 196, 191 (2010). Hyperfine anomaly 85  87 This work (from A HeII ) 0.330 (5) % literature value 0.3474 % difference 5(1) % for the 1st order hyperfine anomaly (Bohr-Weisskopf effect) hyperfine anomaly Electronic level structures are the same among isotopes → same

26. 2010.06.14 APSE2010 Atomic hyperfine structure in He II B ＜ 1% increasement A=   /I ・ J is different in He II Atoms are pressurized by He valence electron orbital is affected HeII (GHz) vacuum (GHz) Hyperfine coupling constatns HeII/vacuum ratio 133 Cs Rb 85 87 2.31283(3)2.29815794 1.01700(3) 3.43514(5) 3.41734131 1.01191092 1.00638(1) 1.00503(3) 1.00521(1) Changes in Cs ＞ Rb B ’ (> B) Pressurized by helium Perturbation for Cs ＞ Rb Preliminary

27. 2010.06.14 APSE2010 Further development optical pumping of atoms other than alkalis In vacuumIn He II Needs many lasers A single laser can excite all the atomic levels Absorption spectra are broadened It is plausible to optical pump atoms with complicated energy levels? Pumping rate  Spin relaxation rate  ・ wavelength do not need to be exactly tuned ・ spin polarization is generated if pumping rate is larger than the relaxation rate ・ pulsed laser can be used as well as cw lasers Taking advantage of characteristic feature of He II freedom to choose lasers Group 11 elements (Ag, Au) are spin polarized

28. 2010.06.14 APSE2010 Outline (1) Advanced atomic photon spectroscopy - Atomic laser spectroscopy - High precision spectroscopy for fundamental physics … nuclear physics (2) Atomic photon spectroscopy in condensed helium - Characteristic of atoms in superfluid helium (He II) - Precision laser spectroscopy of atoms in He II (3) Application of precision laser spectroscopy to atoms with unstable nuclei - Novel nuclear laser spectroscopy of RI atoms in He II : OROCHI (4) Summary

29. 2010.06.14 APSE2010 Laser spectroscopy of atoms in He II for the study of unstable nuclei : “OROCHI” Optical RI-atom Observation in Condensed Helium as Ion-catcher He stopper of RI beam Laser spectroscopy + For the systematic determination of nuclear spins and moments by measuring atomic Zeeman and hyperfine splittings RI beam Laser Ion beam (radioisotope atoms) separator Accelerator RI atoms target LIF He II Advantageous for the study of low yield and short-lived unstable nuclei

30. 2010.06.14 APSE2010 Advantages of using He II for the limited number of accelerator generated nuclei Advantages of laser spectroscopy Advantages of He II matrix + He II ・ high trapping efficiency of He II (expected to be nearly 100 %) Laser ・ observation of LIF photons repeatedly (typically 10 5 /s) ・ no background from the other elements wavelength (nm) Intensity (arb.unit) absorption (broad) in vacuum emission (sharp) 133 Cs in He II ・ characteristic spectra of atoms in He II due to the interaction between atoms and He ・ background of stray light is reduced, by the order of 10 -10 - 10 -13 Detector wavelength: LIF  ≠  laser not really Disadvantage? potentially  1 pps RI atoms < ~

31. 2010.06.14 APSE2010 the first laser experiment @ RIKEN RIPS beam line ・ inject high speed ion beam, and observe laser induced fluorescence from the neutralized atoms D1 D2 F1 F2F3 F2-slit F1-slit Al degrader: 0 um – 700 um (12.5 um step variable) 87 Rb, 66 A MeV, 10 6 pps, Mylar: 6 um F3-PL: 50 um Collimator: 1 cm Kapton: 50 um havar: 25 um Kapton: 50 um Mylar: 6 um 87 Rb primary beam He II RI beam injection cryostat Large solid angle optical detection system variable Al degrader, plastic ・ optical pump & laser RF/MW double resonance 84,86 Rb secondary beam target 1st experiment Towards beam-line experiment 2nd experiment Laser

32. 2010.06.14 APSE2010 87Rb beam Liq. He dewer He II cryostat Pumping system for He II Optical detection system Laser Beam-line experiment setup

33. 2010.06.14 APSE2010 87Rb beam Liq. He dewer He II cryostat Pumping system for He II Optical detection system Laser Beam-line experiment setup experiment is scheduled in Sep. 2010

34. 2010.06.14 APSE2010 Summary ・ The ultimate precision spectroscopic measurements can be a powerful tool to approach the fundamental physics and cosmology, including particle and nuclear physics. ・ Precision spectroscopy of atoms in superfluid helium is possible by using the combination of optical pumping and double resonance spectroscopy. ・ We have successfully demonstrated that superfluid helium provides a new environment of optical spectroscopy through the measurement of long spin relaxation time and the precision laser spectroscopy of Rb and Cs. ・ Laser spectroscopy of atoms in superfluid helium will be a powerful technique to study nuclear structure of short-lived radioisotopes (RIs) generated at accelerator facilities; OROCHI (Optical RI-atom Observation in Condensed Helium as Ion-catcher) project.

35. 2010.06.14 APSE2010 Spokesperson: Takeshi Furukawa (Tokyo Institute of Technology), Yukari Matsuo (RIKEN) RIKEN; H.Ueno, N.Aoi, A.Yoshimi, K. Yoneda, M.Takechi, Y.Togano, Y. Ichikawa, S.Takeuchi, S.Nishimura, M.Nishimura, T. Kobayashi, M.Wada, T.Sonoda, T.Motobayashi … Tokyo Tech.; K.Asahi, Y.Kondo.. CYRIC, Tohoku U.; A. Sasaki, T.Wakui, H.Ouchi, S.Izumi, T. Shinozuka Osaka U.; T. Shimoda, A.Odahara Tokyo U. Agr. Tech.: A. Hatakeyama Meiji U.: Y. Matsuura, Y. Kato, Y. Yamaguchi, K. Imamura Aoyama-gakuin U.: A.Takamine CNS, U.Tokyo; S.Kubono, Y. Ohshiro … Acknowledgement to OROCHI collaborators

36. Thank you for your attention !