Cold and slow molecular beams: Application to electron electric dipole moment (EDM) measurements Katsunari Enomoto, Univ. of Toyama Fundamental Physics Using Atoms 2010 2010/Aug/9 Osaka U. Electron electric dipole moment spin electron spin EDM T, P EDM related with CP, T violation physics Standard model electron EDM de 10-38 e cm SUSY, left-right, multi-Higgs de < 10-24 e cm Experiment (Tl atomic beam) de < 10-27 e cm PRL 88, 071805 (2002). Table-top experiment for the physics beyond the standard model. EDM measurement using atoms E // B Typical atomic beam method E // B or S precession Eappl0.1 MV/cm B1 nT t Due to the relativistic effect, heavy atoms have large enhancement factor R. (Cs: R110, Tl: R590, Fr: R1150) h B Eeff = R Eappl 0.1 GV/cm, de Eeff / h 10 Hz m=1/2 m=1/2 False EDM signal (systematic error) Leak current loop v E induced field v I E EDM measurement using molecules atom molecule Induced dipole |p Eeff elec. mix with Eappl permanent dipole |J=1 Emol rot. |J=0 mix with Eappl |s Eeff = R Eappl 0.1 GV/cm, with Eappl 0.1 MV/cm Eeff = P Emol 10100 GV/cm, P 1 with Eappl 0.01 MV/cm (Eappl is needed just for aligning molecule) Sensitivity 1001000 Systematic error 0.1 Atoms vs molecules Tl beam experiment PRL 88, 071805 (2002). de < 10-27 e cm Why is it not so good? Vibration (1000 K) Rotation ( 1K) YbF beam experiment vs PRL 89, 023003 (2002). de < 10-25 e cm …. because radical molecular beams are difficult to produce, and molecules have many internal levels (especially rotation). Cold (large population in the ground state) and slow (long interaction time) molecular beam will improve greatly the sensitivity. In this talk, after reviewing cold molecule experiments, I will present our recent results and ongoing projects. Ultracold molecules Ultracold molecules are one of the hottest topics in atomic/molecular/optical (AMO) physics in this decade. High resolution spectroscopy New condensed matter Test of fundamental physics Quantum simulator Direct cooling of molecules (mK) Ultracold chemistry Control of chemical reaction Laser cooling of atoms and associating to molecules (nK) Direct cooling methods (1) Supersonic expansion is a conventional method for molecular spectroscopy, and it generates cold (1 K) but fast (supersonic) molecular beams. How to slow down? Stark decelerator & electrostatic trap Bethlem et al., Nature 406, 491 (2000). Counter-rotating nozzle Gupta et al, J. Phys. Chem. A 105, 1626 (2001) Direct cooling methods (2) Laser ablation can generate molecular gases in cryogenic helium gas (1 K). Effusive molecular beam Maxwell et al., Phys. Rev. Lett. 95, 173201 (2005) Buffer-gas cooling & magnetic trap Weinstein et al., Nature 395, 148 (1998) Hydrodynamically enhanced-flux (but boosted to 160 m/s) molecular beam Patterson et al., J. Chem. Phys. 126, 154307 (2007) Control of translational motion Now, molecules can be cooled/decelerated down to 1 K. Many tools are available to control molecular translational motion, e.g. electric & magnetic static field, optical field, … Our approach: using microwave field Stark shift of diatomic molecules Advantage of microwave: DeMille et al, Eur. Phys. J. D 31, 375 (2004) Energy High-field-seeking (HFS) ground state can be trapped. LFS J=1, m=0 HFS J=1, |m|=1 J=m=0 HFS state cannot be trapped with static fields due to Earnshaw’s theorem. Electric field Microwave trap for molecule It has been proposed to a microwave field enhanced in a Fabry-Perot cavity to trap polar molecules. For static field (dc Stark shift) (J=0,1 states) 2B dE / 3 H dE / 3 0 DeMille et al, Eur. Phys. J. D 31, 375 (2004) Electric field E (P Q)1/2 For microwave field (ac Stark shift) dE / 2 3 r H 0 dE / 2 3 2B: rotational splitting : detuning d : dipole moment of molecule Assuming power P 2 kW, quality factor Q 105, Electric field E 30 kV/cm ( 3 K trap depth) is possible. Microwave Stark decelerator We proposed that HFS state molecules can be decelerated by using time-varying standing wave of microwave. Enomoto & Momose, PRA 72, 061403 (2005) Current plan: to use circular waveguide resonator TE11 mode TE11 Potential w/ microwave Alternate gradient focusing decelerator Bethlem et al., PRL 88, 133003 (2002) Tarbutt et al., PRL 92, 173002 (2004) More powerful, but dynamical radial confinement Radial confinement for HFS state Potential w/o microwave Simulation of deceleration L 1000 Molecule : Initial velocity : 21 – 24 m/s Center molecule : 22.5 m/s (5.8 K) Deceleration : 93 cm, 80 ms P[W] Q : 107 Molecules 174YbF 800 600 400 200 0 23.0 0.2 0.4 0.6 0.8 1.0 Distance (m) 20 40 Time (ms) 60 80 Initial velocity (m/s) Velocity (m/s) 0 25 20 15 10 5 0 0.0 25 20 15 10 5 0 0 5 10 15 20 25 Final velocity (m/s) 22.8 22.6 22.4 22.2 22.0 -4 -3 -2 Initial position (mm) Microwave Stark decelerator can be used for molecular beams pre-cooled to about 5 K. -1 First experimental step: microwave lens w/o microwave Molecular beams can be focused with a microwave field. w/ microwave Performed in Fritz-Haber institute by using a decelerated NH3 beam Odashima et al., PRL 104, 253001 (2010) Next plan for microwave control Electric field E2 (power P) (quality factor Q) High P needs expensive amps and causes heating. So we are planning to use a superconducting cavity for high Q. (Q factor is mainly determined by the surface resistance.) Lens exp. (Cu cavity) Power P[W] 3 SC cavity (Nb or Pb/Sn) <3? Q-factor 5000 3106 ? PQ 1.5 104 107 ? Limited by cooling power (Note that only 0.1 s is needed for deceleration.) Q > 106 is typically easily obtained, but we have to rapidly switch microwave. This limits the Q factor. We will test the superconducting cavity soon in U. British Columbia (Momose lab.) Project in Univ. of British Columbia We are constructing a Stark decelerator in UBC. We will combine the Stark decelerator with superconducting cavity. Testing a microwave resonator Firstly, we tested a copper resonator with a loop antenna. loop antenna Transmission room temperature FWHM = 2.92 MHz 0.8 0.6 0.4 Cool down with L.N2 Q factor 3 1.0 QL 16000 L. N2 temperature FWHM 1.07 MHz 0.8 Transmission QL 5000 1.0 0.6 0.4 0.2 0.2 0.0 785 790 795 Frequency - 14000 (MHz) 0.0 680 685 690 Frequency - 16000 (MHz) We will test a Pb/Sn-coated superconducting cavity soon. Project in Univ. of Toyama We are making cold molecular beams based on He buffer-gas cooling. L. He bath He gas line To mass spectrometer Laser ablation (pulsed green laser) exit hole sorption pump We have observed Pb and O atoms produced by laser ablation of a PbO target with mass spectrometer. EDM measurement project We are starting the EDM measurement project in Univ. of Toyama from this year. Only the project plan is presented here. What molecules? How to produce molecules? How to cool them to a few K? How to enhance the flux? What more? Choice of molecule unpaired electron Heavy atom Large electronegativity To obtain high beam flux in a single internal state Low boiling point (even for laser ablation) Small nuclear spin (simple hyperfine structure) large natural abundance From experimental point of view Less toxic Not radioactive Tentative plan: to use YbF (like E. Hinds group, Eeff = 26 GV/cm) or BaF (Eeff = 8 GV/cm) low density and directionality high Cooling procedure Supersonic jet room T Initial velocity is determined by carrier gas e.g. YbF in Xe 300 m/s corresponds to 1000 K for YbF Hydrodynamic He buffer-gas-cooled beam Initial velocity is determined by He gas (160 m/s 300 K for YbF) 4 K, high He density Effusive He buffer-gas-cooled beam Initial velocity is determined by the cell temperature ( 4 K) 4 K, low He density We will use He buffer-gas-cooled beam close to effusive regime. Improvement of flux How to generate molecules? Laser ablation Injection from oven oven 1012 /pulse poor reproducibility 1015 /s ? (like J. Doyle group) How to improve directionality? Microwave lens Laser cooling (SrF: Shuman et al., PRL 103, 223001 (2009).) They also help isotope selection suppression of background noise Future possibility Microwave deceleration and trap Combination of alternate gradient decelerator and microwave decelerator Conclusion Microwave enhanced in resonators is available to control molecular translational motion (such as deceleration and trap). As a first step, we demonstrated the microwave lens. Odashima et al., PRL 104, 253001 (2010) We will test soon a high-Q superconducting resonator. For electron EDM measurement, we are making He-buffer-gasbased cold molecular beam (YbF or BaF). EDM measurement with molecular beams with cold molecule technologies developed in this decade is promising. Acknowledgments Microwave lens experiment H. Odashima, S. Merz, M. Schnell, G. Meijer (Fritz-Haber-Institut) Superconducting cavity project O. Nourbakhsh, P. Djuricauin, T. Momose, W. Hardy and his students (Univ. of British Columbia) Buffer-gas cooled beam project Y. Kuwata, H. Noguchi, H. Hasegawa, S. Tsunekawa, K. Kobayashi, F. Matsushima, Y. Moriwaki (Univ. of Toyama) And courtesy of D. DeMille 77K shield 分子ビーム 4K shield チャコール セル マイクロ波定在波 TE11 TE01 マイクロ波定在波あり マイクロ波定在波なし Fabry-Perot TEM00 光ポンピング B state Diode J’=1 laser J=1 X state J=0 マイクロ波 トラップ pump He gas L. He Q-mass PbO pump pulse YAG pump pump シュタルク ガイド LFS HFS Bethlem et al., PRA 65, 053416 (2002). Stark UBC Microwave Lens deceleration (collimation) Buffer gas Cold slow beam Toyama trap EDM measuremen Acknowledgment FHI UBC Toyama Atoms or molecules? atom vib. molecule Induced dipole elec. mix with Eappl rot. Large internal electric field (Eeff 10 GV/cm) Easy to handle High electric field Eappl is needed (causing systematic error) Eeff 500 Eappl, Eappl 100 kV/cm mix with Eappl to align molecule Rotation and vibration exist (small population in the ground state at room temperature, which reduce statistical certainty) Experiment (Tl atomic beam) de < 10-27 e cm Experiment (YbF molecular beam) de < PRL 88, 071805 (2002). 10-25 e cm PRL 89, 023003 (2002). Cold molecular beam (or trapped molecules) will improve much more.