21aCM-7 レーザー冷却を応用した^ Ca^+イオン蓄積方の開発II

Marko Gacesa, Robin Côté

We investigate ultracold collisions of heteroisotopic pairs of Ca with Ca + mediated by an external magnetic field. Based on the nuclear spin of Ca, namely I = 7/2 for 43 Ca and I = 0 for other isotopes, we identify different scattering dynamics and characterize magnetic Feshbach resonances in 43 Ca+ 43 Ca + and 43 Ca+ (40,42) Ca + collisions. Our results suggest that interisotopic Feshbach resonances could be used to control charge-exchange in ultracold atom-ion mixtures of Ca and its ion.

優紀 岡野, 英幸 澤村, 健二 豊田 +1 more

脩 長沼, 健太郎 大伊, 篤郎 盛永

Jicai Zhang, Jinfeng Sun, Zunlue Zhu +1 more

The s-wave scattering lengths are obtained for all stable isotope combinations of Ca atoms and those values are very sensitive to small changes of the reduced mass. These results rely on a recent measurement of the 40 Ca– 40 Ca scattering length in a Bose condensate of 40 Ca and making small corrections to a Born–Oppenheimer potential that reproduces all known spectroscopic data. We find that the 42 Ca isotope has a scattering length of 417.5 a 0 and, thus, can be Bose condensed. The large interisotope scattering length between 43 Ca and 42 Ca indicates that sympathetic cooling of 43 Ca by 42 Ca atoms will be effective, and 43 Ca– 42 Ca can also be used to study isotopic Bose–Fermi mixtures. We also predict a d-wave shape resonance for collisions of fermionic 43 Ca atoms in different spin components.

David Husain, Gareth O. Roberts

Two separate series of investigations have been carried out on the optically metastable states Ca[4s4p(3PJ)] and Ca[4s3d(1D2)], generated by pulsed dye-laser excitation at λ= 657.3 nm {Ca[4s4p(3P1)]â†� Ca[4s2(1S0)]} and λ= 457.5 nm {Ca[4s3d(1D2)]â†� Ca[4s2(1S0)]}, with particular emphasis on energy pooling. The kinetic behaviour of these two states has been characterised in detail across a wide range of temperature and pressure by time-resolved atomic emission measurements at the resonance wavelengths. In the case of Ca[4s3d(1D2)] these represent the first time-resolved measurements on this atomic state, yielding a mean radiative lifetime for emission to all lower states of τe= 1.71 ± 0.03 ms, in accord with time-of-flight measurements in atomic beams. The measured temperature dependence of the diffusion coefficient D12[Ca(4 1D2)–He], when expressed in the form D12∝Tn, yielded n= 1.77 ± 0.08. Further, the rate constant for the collisional quenching of Ca(4 1D2) by Ca(4 1S0) itself is estimated to be kCa=(4 ± 3)× 10–14 cm3 atom–1 s–1, in sensible accord with similar data for the quenching of Ca(4 3PJ) by the ground-state calcium atom. Energy pooling between Ca(4 3PJ)+ Ca(4 3PJ) is shown to give rise directly to Ca[4s4p(1P1)] and Ca[4s3d(1D2)]. Energy pooling between Ca(4 1D2)+ Ca(4 1D2) is shown to yield 22 electronic states, each of whose kinetic behaviour was characterised quantitatively from the relevant atomic emission profiles, including measurement of relative atomic yields.

直樹 木村, 皓一 椎名, 俊暢 高柳 +3 more