高精度分光を目指した CaH + の 生成とトラップ 富山大学・理 森脇喜紀

Spectroscopy of 40 CaH + the pure vibrational transition (v=0, J=0, F=1/2, M=±1/2) → (v=1, J=0, F=1/2, M=±1/2) can potentially be measured with an uncertainty of by use of simultaneous trapping with Ca + ions sympathetic cooling quantum logic measurement Application to the test of the time invariance of fundamental constants e.g. electron-proton mass ratio { P.O.Schmidt et al. Science 309, 749(2005) Motivation Shelkovnikov et al. PRL100, (2008) Vibrational transition of SF 6  ～

v = 1 v = 0 J = 0 F = 1/2 J = 1 F = 1/2 J = 1 F = 3/2 magnetic field f+f+ f-f- M = 1/2 M = -1/2 couplings induced by probe laser ＊ J = 0 – 0 transition possible ＊ Stark shift is induced | f + - f - | < 1.2 x Hz/T f = THz (7.1μ m) CaH + 1  state

Proposal: High precision measurements of the pure vibrational transition of 40 CaH + Simultaneous trapping of a 40 CaH + and a 40 Ca + in a linear trap Long interaction time reduces the homogeneous linewidth Ions in a crystal state inside a linear trap are free from Stark shift Some transition frequencies of molecular ions are free from Zeeman shift Kajita and Moriwaki J. Phys. B 42, (2009)

Estimated frequency uncertainty (order of ) CaH + （ v = 0, J = 0, F = 1/2, M = ± 1/2 ） → （ v = 1, J = 0, F = 1/2, M = ± 1/2 ） transition f = THz (7.1  m) (1) Natural linewidth 2.5 Hz (2) Zeeman shift (magnetic field < 1 G) < 1.3 x (3) Stark shift induced by the trapping electric field < (4) Electric quadrupole shift is zero because of F = 1/2 (5) Stark shift induced by probe laser light is most dominant ~ 1.2 x with saturation power (32 mW/cm 2 )

Georgiadis et al. J. Chem. Phys. 92, 7060 (1988) 2.5 eV Production of CaH + endothermic reaction Ca + (4p 2 P 1/2 ) + H 2  CaH + + H ? (2) Ca + +H 2 → CaH + +H (1) Laser ablation of Ca containing solids

Laser system To Trap Pump laser (397 nm) Repump laser (866 nm)

RF Trap Hyperboloid electrodes r 0 =7.5 mm V dc =0 V V ac =350 V Ω/2π=1.65 MHz D z =25 eV V dc +V ac cos Ωt

LIF dependence on He pressure and q z

Temperature and size of ion cloud Doppler width ~2 GHz T~600 K Δr~0.45 mm Δz~0.23 mm

LIF decay with H 2 buffer gas LIF signal is proportional to the number of Ca + ions. With H 2 buffer gas, LIF decay significantly. Ca + (4p 2 P 1/2 )+H 2 →CaH + +H ?  ~3600 s  ~11000 s

Q-Mass spectrum Buffer gas : H 2 ( %) The mass signal (m=41u) is normalized by that of m=40 u M=41u signals appear with the laser irradiation. With D 2 buffer gas, m=42 u signals are observed. Production of CaH +, CaD + has been confirmed !

Indication of some loss mechanisms of Ca + Without 397nm and 866nm laser, LIF decays slowly. Without 866 nm laser, LIF decays fast although the 2 D 3/2 state is optically pumped. Ca + (3d 2 D 3/2 ) + H 2  CaH + + H / Photoassociated ion loss?

spectroscopy of CaH + There have been no experimental data on CaH +. Needs for reliable theoretical data ab initio calculations of Ca + -H potential curves electric energy levels, vibrational levels, Rotational constants, transition dipole moments by M. Abe (collaborator)

Ca + 2 S [(4s) 1 ] + H 2 S [(1s) 1 ] Ca + 2 D [(3d) 1 ] + H 2 S [(1s) 1 ] Ca + 2 P [(4p) 1 ] + H 2 S [(1s) 1 ] Potential energy curves

a 4th order MBPT: Canuto et al. Phys. Rev. A b Two-elec. valence CI and core polarization: Boutalib et al. Chem. Phys Spectroscopic constants of the ground state of CaH + (1 1  )

Vibrational TDM in atomic unit (2 1  )

2121 3131 AbsorptionEmission 2 1 S statearound 400nmmore than 600nm 3 1 S state240 nm400 nm 2 1 P state240 nm380 nm Candidate transitions in LIF

Conclusion We proposed high precision measurements of the pure vibrational transition of 40 CaH + production of CaH +, CaD + is confirmed Future laser spectroscopy of CaH + Cryogenic ion trap: 99% of CaH + ions are localized in the (v,J)=(0,0) state at T=4 K H 2 vapor pressure ~ Torr

共同研究者 梶田雅稔 (NICT) 阿部穣里 (Tokyo Metropolitan Univ.) 松島房和, 小林かおり, 榎本勝成 ( 富山大学 ) 小山達也, 中口利彦, 日比野誠 ( 学生 )