Laser Spectroscopy of RI atoms stopped in superfluid helium “OROCHI” (Optical RI atom Observation in Condensed Helium as Ion-catcher) Laser Spectroscopy of RI atoms stopped in superfluid helium “OROCHI” (Optical RI atom Observation in Condensed Helium as Ion-catcher) Florence, Italy /2-7 Takeshi Furukawa Tokyo Metropolitan University from “DRAEMON” vol. 22, by FUJIKO, F. Fujio

“ OROCHI ” Optical RI-atom Observation in Condensed Helium as Ion-catcher Laser Ion beam > 50 MeV/u Separator (i.e. BigRIPS in RIKEN) (i.e. BigRIPS in RIKEN) Accelerator (i.e. SRC in RIKEN) (i.e. SRC in RIKEN) RI beam Target Laser Induced Fluorescence He II (((((((((((( RadiowaveorMicrowave Zeeman structure Hyperfine structure Nuclear spin Nuclear moment What is “OROCHI” ? INPC2013, /2-7, T. Furukawa To measure the nuclear spins & moments in exotic nuclei “Laser spectroscopy in superfluid helium (He II)” “Laser spectroscopy in superfluid helium (He II)” - Nuclear Laser spectroscopy: effective, … but difficult for low yield exotic RIs. effective, … but difficult for low yield exotic RIs.

Laser Detector wavelength: LIF  ≠  laser Suppress background count Reduction: He II Advantage in He II 光波長 (nm) Intensity (arb.unit) 133 Cs atomic spectra in He II ① largely blue-shifted ( in vacuum emission ② widely broadened Wavelength (nm)also Atomic absorption spectra in He II to reduce the b.g. photons. absorption We use He II to trap the atoms efficiently, INPC2013, /2-7, T. Furukawa

B laser atoms m = -1/2m = +1/2 S 1/2 P 1/2 σ+σ+ X D1 Line σ+σ+ m = +3/2 Measurement of atomic sublevel structure ： Double resonance spectroscopy ： Double resonance spectroscopy In the case of Zeeman splitting in alkali atoms m = -1/2m = +1/2 S 1/2 P 1/2 σ+σ+ X σ+σ+ m = +3/2 1 st step : optical pumping 2 nd step: double resonance m = -1/2m = +1/2 S 1/2 P 1/2 σ+σ+ X D1 Line σ+σ+ m = +3/2 rf-resonance (((((((((((( (((((((((((( rf I LIF rf frequency / Magnetic field Expected spectrum Double resonance spectroscopy No level INPC2013, /2-7, T. Furukawa [I LIF ] ∝ 1 - P z decreased gradually (LIF : Laser Induced Fluorescence) LIF Intensity…

INPC2013, /2-7, T. Furukawa Introducing atoms in He II by laser sputtering Stable isotopes of Rb, Cs, Ag and Au So far, feasibility test with stable isotopes

atomic sublevel structure Zeeman splittings Zeeman resonance of Rb isotopes Δ Zmn = g F m B B / h 2.8 (MHz) ×B (Gauss) = (2I+1) Nuclear spin I 85Rb = 2.6(1) → 5/2 I 87Rb = 1.55(5) → 3/2 hyperfine splitting This work (from A HeII ) evaluated (from A vacuum ) literature value (NMR)  I 85Rb (  N ) (7)  N (1)  N  N Hyperfine resonance of 85 Rb Nuclear spin & moment determination INPC2013, /2-7, T. Furukawa Polarization ： ~90 % (Cs), ~40 %(Rb) Polarization ： ~90 % (Cs), ~40 %(Rb) ~85 % (Ag and Au) T. F. Doctoral thesis, Osaka Univ. (2007) T. F., Hyperfine Interactions 196, 191 (2009)

Feasibility test with Rb ion beams Rb beam laser cryostat Photo-detection system Rb beam from RIPS pps = 0.01pnA pps = 0.01pnACryostat Photo-detection system - large Fresnel lens x 3 - large Fresnel lens x 3 - Interference filter x 2 - Interference filter x 2 - Cooled Photomultiplier tube - Cooled Photomultiplier tube INPC2013, /2-7, T. Furukawa 84, 85 Rb (< 50 MeV/u) from RIKEN RIPS beam line Next step: Using energetic ion beams

Ti:Sa Laser 780nm, 100mW 780nm, 100mWOptical window window Optical B 0 coil Rb beam RF coil T He = 1.8 K Inner Cryostat INPC2013, /2-7, T. Furukawa Havar foil (20  m) (20  m)

Observed spectra (preliminarily) INPC2013, /2-7, T. Furukawa 84 Rb, I  = Rb, I  =5/2 - ? 84 Rb m, I  =6 - ? 85 Rb, I  =5/2 - Peak with B = 0 85 Rb: 8.6 x 10 4 pps, 15 min. measurement 15 min. measurement Frequency 1.5 MHz Frequency 1.5 MHz 84 Rb: 5.7 x 10 4 pps, 30 min. measurement 30 min. measurement Frequency: 1.0 MHz Frequency: 1.0 MHz By sweeping applied magnetic field strength (not the frequency of radiowave) (not the frequency of radiowave) B = 0: Atoms can not conserve their polarization Atoms can not conserve their polarization All the atoms can emit the LIF All the atoms can emit the LIF

Improvement for the next experiment Small resonance peak: due to insufficient rf power due to insufficient rf power absorbed to the metallic beam window absorbed to the metallic beam window (Stainless steel and Havar) (Stainless steel and Havar) Made new beam window by non-metallic FRP and Kapton foil by non-metallic FRP and Kapton foil Next experiment: scheduled on next month for measuring the hyperfine/Zeeman structures of 84,86 Rb for measuring the hyperfine/Zeeman structures of 84,86 Rb - required RI yields: pps - required RI yields: pps 85 Rb

Summary & Future “ OROCHI ” Optical Radioisotope-atom Observation in Condensed Helium as Ion-catcher ・ We developed the new laser spectroscopy method “OROCHI” for exotic RIs far from stability, by using superfluid helium (He II) as a stopper of RI beam and host matrix of laser spectroscopy. ・ We have successfully demonstrated the feasibility with energetic RI beams. Zeeman resonances from 84,85 Rb atoms injected into He II whose intensity as the order of 10 4 pps have been observed. ・ Next, we will measure the hyperfine structure of radioisotope 84,86 Rb in He II in next month. After that we will apply it to exotic RI of feasible elements, for example Ag, Au and Fr in near future. ・ We will upgrade some of our experimental setups and improve the overall efficiency. The required RI intensity for one-day measurement is now estimated as 10 3 pps. We will reduce it to less than 10 pps with the improvement of setups. INPC2013, /2-7, T. Furukawa

RIKEN ： X.Yang, H. Ueno, Y. Ishibashi, M. Wada, T. Sonoda, Y. Itou, T. Kobayashi, S. Nishimura, M, Nishimura, K. Yoneda, S. Kubono Osaka Univ.: T. Fujita, T. Shimoda CYRIC, Tohoku Univ.: T. Wakui, T. Shinozuka Meiji Univ.: K. Imamura, Y. Yamaguchi, Y. Mitsuya, S. Arai, M. Muraoka Tokyo Univ. of Agriculture and Tech. ： A. Hatakeyama Spokesperson: Takeshi Furukawa (Tokyo Metropolitan University), Yukari Matsuo (Hosei University) CNS, Univ. Tokyo: Y. Oshiro Tokyo Gakugei Univ.: H. Tetsuka, Y.Tsutsui, Y. Ebara, M. Hayasaka, Tokyo institute of Technology: Y. Ichikawa, K. Asahi, N. Yoshida, H. Shirai, Y. Kondo Collaboration INPC2013, /2-7, T. Furukawa

Thank you for your attention. INPC2013, /2-7, T. Furukawa

＋ e-e-e-e- He II absorbradiate deform deform ・ Need more energy → blue shifted abs. spectrum ・ Different atom-He distance → broadened spectra ground state state Atom-He distance Energy potential excited state state Atomic Spectra in He II INPC2013, /2-7, T. Furukawa

Preliminarily B.G. from stray laser light INPC2013, /2-7, T. Furukawa B.G. from unpolarized atoms - Increase rf power - Reduce remaining stray laser light - Reduce stray magnetic field - Reduce convection flow in He II - Increase polarization of atoms

Optical-Detected Magnetic Resonance (applying RF with the frequency 2 MHz) B coil B room B B B coil B B coil : Max = Large polarization B coil : 0 = Small polarization B coil max B coil 0 time LIF intensity Coil current B coil : h rf /g F  B = Resonance (((((((((((( (((((((((((( rf B Sweeping magnetic field strength… With applying rf field … In the case of stable Au atoms INPC2013, /2-7, T. Furukawa Preliminarily

Optical pumping in He II Polarization ： ~90 % (Cs), ~40 %(Rb) ~85 % (Ag and Au) Polarization switched (in the case of Cs atoms) Linearly polarized Circularly polarized T. Furukawa et al., Phys. Rev. Lett. 96, (2006) Produce the polarization on stable isotopes in He II Polarization: increased LIF intensity: decreased T. Furukawa et al., Physica E 43, 843 (2011) INPC2013, /2-7, T. Furukawa

Feasibility test with Rb ion beams Rb beam laser cryostat Photo-detection system INPC2013, /2-7, T. Furukawa 84, 85 Rb (< 50 MeV/u) from RIKEN RIPS beam line Next step: Using energetic ion beams