The 4th Yamada Symposium on Advanced Photons and Science Evolution 2010 APSE 2010 2010.06.14

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

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

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

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

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

State-of-the-art experiment

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

S magnetic field s=½ L J I nuclear spin Orbital angular momentum 2D5/2 D 2D3/2 2P3/2 L+S=J P 2P1/2 L≧1 levels split due to spin-orbit interaction (LS-coupling) D2 D1 2S1/2 S ＝0 ＝1 ＝2 Zeeman splitting Hyperfine structure Fine-structure e.g. splitting of D line in Na atom atom HFS for unstable 7Be+ is measured A = 742.772 28(43) MHz by RIKEN SLOWRI group Nuclear moments Nuclear spins Laser light K. Okada, et.al.,PRL 101, 212502 (2008) emission Atomic laser spectroscopy and the study of nuclei alkaline –like atoms Nuclear laser spectroscopy Precision measurement of atomic sublevel structures can provide valuable information on nuclear structure because nuclear spins and moments are fundamental physical quantities of nuclei

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

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 ?

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

absorption emission relaxation ＋ e- He II deform bubble radius energy absorption deform Optical spectra (atomic-bubble model) sharp, small shift broad, large blue-shift simple model describes spectra well

emission Ba+ D1 spectrum 650nm 2P3/2 2P1/2 2P3/2 2P1/2 650nm line position in vacuum D1 D1 2D5/2 493nm 894nm 2D3/2 2S1/2 2S1/2 absorption (broad) energy level in vacuum 493nm Heidelberg group Reyher, et.al., 1986 Typical LIF spectra of atoms/ions in He II Cs D1 spectrum line position in vacuum 133Cs in He II Intensity (arb.unit) energy level in vacuum absorption (broad) wavelength (nm) emission (sharp) Kyoto group Takahashi, et.al., 1993

atoms observed ions observed Atoms and ions observed using laser spectroscopic method in He II

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

Optical pumping with circular polarized light P1,0 potential energy Laser s+ population accumulated M sub-levels excitation emission sharp, small shift broad, large blue-shift S0,0 rHe-M Using superfluid helium as a matrix … • large shift, broad spectrum could be an obstacle Multiple HFS levels can be optical pumped simultaneously HFS transition is observable using laser – microwave double resonance for Cs Takahashi, et.al. Z. Phys. B 98 (1995) 391 introducing atoms quietly was difficult...

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

excited state electronic transition is perturbed by surrounding He Zeeman splittings ground state hyperfine splitting atomic sublevel structures not much affected expected spectrum LIF decreases Optical pumping Double resonance spectroscopy F=1 F=1 mF= -1 0 +1 mF= -1 0 +1 F=1 2P1/2 2P1/2 mF= -1 0 +1 2P1/2 F=0 F=0 0 LIF intensity 0 F=0 0 X circularly polarized laser light X X F=1 F=1 mF= -1 0 +1 mF= -1 0 F=1 2S1/2 2S1/2 +1 mF= -1 0 +1 2S1/2 F=0 MW or RF frequency F=0 RF 0 0 F=0 0 LIF increases MW Double resonance spectroscopy Mearsurement of atomic sublevel structures

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

atomic sublevel structure Zeeman splittings ・ Zeeman splittings （Rb isotope, 4 Gauss） nuclear spins I85Rb = 2.6(1) → 5/2 I87Rb = 1.55(5) → 3/2 Zeeman splittings (alkali atoms, s-state) ΔEZmn= gFmB B 2.8(MHz)×B(Gauss) h = (2I+1) T. Furukawa, Doctoral thesis, Osaka Univ. (2007) T. Furukawa, et. al., Hyp. Int., 196, 191 (2010). Zeeman splitting measurement

atomic sublevel structure Zeeman splittings hyperfine splitting Electronic level structures are the same among isotopes → same hyperfine resonance: width-50kHz Precision measurement of hyperfine structure ・ hyperfine structures （Cs, Rb isotopes） mI85Rb (mN) magnetic moment 同位体：　電子構造が同じ →が同じ 1.357 83 (7) mN This work (from AHeII) ・ determine nuclear moments 1.358 071(1) mN ・ as accurate as in vacuum evaluated (from Avacuum) 1.353 351 5 mN literature value T. Furukawa, Doctoral thesis, Osaka Univ. (2007) T. Furukawa, et. al., Hyp. Int., 196, 191 (2010). Hyperfine splitting measurement

atomic sublevel structure Zeeman splittings hyperfine splitting Electronic level structures are the same among isotopes → same hyperfine resonance: width-50kHz Precision measurement of hyperfine structure mI85Rb (mN) magnetic moment 同位体：　電子構造が同じ →が同じ 1.357 83 (7) mN This work (from AHeII) 1.358 071(1) mN evaluated (from Avacuum) 1.353 351 5 mN literature value Hyperfine anomaly hyperfine anomaly for the1st order hyperfine anomaly (Bohr-Weisskopf effect) T. Furukawa, Doctoral thesis, Osaka Univ. (2007) T. Furukawa, et. al., Hyp. Int., 196, 191 (2010).

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

Pumping rate G Spin relaxation rate g Further developmentoptical pumping of atoms other than alkalis Taking advantage of characteristic feature of He II In vacuum In He II Absorption spectra are broadened A single laser can excite all the atomic levels Needs many lasers It is plausible to optical pump atoms with complicated energy levels? ・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 freedom to choose lasers Group 11 elements (Ag, Au) are spin polarized

separator RI atoms Ion beam (radioisotope atoms) target Accelerator RI beam He II Laser + He stopper of RI beam Laser spectroscopy LIF For the systematic determination of nuclear spins and moments by measuring atomic Zeeman and hyperfine splittings Laser spectroscopy of atoms in He II for the study of unstable nuclei : “OROCHI” OpticalRI-atomObservationinCondensedHeliumasIon-catcher Advantageous for the study of low yield and short-livedunstable nuclei

・ observation of LIF photons repeatedly (typically 105 /s) ・ high trapping efficiency of He II (expected to be nearly 100 %) ・ no background from the other elements ・ characteristic spectra of atoms in He II due to the interaction between atoms and He He II Laser in vacuum 133Cs in He II emission (sharp) Intensity (arb.unit) absorption (broad) Detector Disadvantage? wavelength:lLIF≠llaser not really ・ background of stray light is reduced, by the order of 10-10 - 10-13 < ~ wavelength (nm) potentially 1 pps RI atoms Advantages of using He II for the limited number of accelerator generated nuclei Advantages of laser spectroscopy Advantages of He II matrix +

Towards beam-line experiment the first laser experiment @ RIKEN RIPS beam line ・inject high speed ion beam, and observe laser induced fluorescence from the neutralized atoms Al degrader: 0 um – 700 um (12.5 um step variable) ・optical pump & laser RF/MW double resonance 1st experiment F2 F3 D2 87Rb primary beam RI beam injection cryostat He II variable Al degrader, plastic F1 F2-slit Kapton: 50 um Laser Mylar: 6 um F1-slit Large solid angle optical detection system D1 Collimator: 1 cm 84,86Rb secondary beam F3-PL: 50 um Kapton: 50 um Mylar: 6 um 2nd experiment target havar: 25 um 87Rb, 66 A MeV, 106 pps,

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

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

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.

Acknowledgement to OROCHI collaborators 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 …

Thank you for your attention !

The 4th Yamada Symposium on Advanced Photons and Science Evolution 2010 APSE 2010 2010.06.14