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arXiv:1310.7264 · Physical Review A

Properties of the ground 3F2 state and the excited 3P0 state of atomic thorium in cold collisions with He3

Yat Shan Au, Colin B. Connolly, Wolfgang Ketterle, John M. Doyle

Published Sep 3, 2014• 4 citations
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Abstract

Inelastic cross sections for collisions between thorium (Th) and helium ($^{3}\mathrm{He}$) are measured. For Th[${}^{3}{F}_{2}$]--$^{3}\mathrm{He}$, we determine the ratio of momentum transfer to Zeeman relaxation cross sections to be $\ensuremath{\gamma}\ensuremath{\sim}500$ at 800 mK. For Th[${}^{3}{P}_{0}$]--$^{3}\mathrm{He}$, we find no quenching of this metastable state during ${10}^{6}$ collisions. We measure the radiative lifetime of Th[${}^{3}P{}_{0}$] to be $\ensuremath{\tau}>130$ ms. The observed stability of Th[${}^{3}{P}_{0}$] opens up the possibility of trapping this metastable species.

DOI
10.1103/physreva.90.032702

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Inelastic cross sections for collisions between thorium (Th) and helium (3He^{3}\mathrm{He}3He) are measured. For Th[3F2{}^{3}{F}_{2}3F2​]--3He^{3}\mathrm{He}3He, we determine the ratio of momentum transfer to Zeeman relaxation cross sections to be \ensuremathγ\ensuremath∼500\ensuremath{\gamma}\ensuremath{\sim}500\ensuremathγ\ensuremath∼500 at 800 mK. For Th[3P0{}^{3}{P}_{0}3P0​]--3He^{3}\mathrm{He}3He, we find no quenching of this metastable state during 106{10}^{6}106 collisions. We measure the radiative lifetime of Th[3P0{}^{3}P{}_{0}3P0​] to be \ensuremathτ>130\ensuremath{\tau}>130\ensuremathτ>130 ms. The observed stability of Th[3P0{}^{3}{P}_{0}3P0​] opens up the possibility of trapping this metastable species.
Inelastic cross sections for collisions between thorium (Th) and helium ([superscript 3]He) are measured. For Th[[superscript 3]F[subscript 2]]–[superscript 3]He, we determine the ratio of momentum transfer to Zeeman relaxation cross sections to be γ ∼ 500 at 800 mK. For Th[[superscript 3]P[subscript 0]]–[superscript 3]He, we find no quenching of this metastable state during 10[superscript 6] collisions. We measure the radiative lifetime of Th[[superscript 3]P[subscript 0]] to be τ > 130 ms. The observed stability of Th[[superscript 3]P[subscript 0]] opens up the possibility of trapping this metastable species.
We measure inelastic cross sections for atomic thorium (Th) and molecular thorium monoxide (ThO) in collisions with 3^33He at temperatures near 1 K. We determine the Zeeman relaxation cross section for Th (3^33F2_22​) to be sim2times10−17\\sim 2 \\times 10^{-17}sim2times10−17~cm−2^{-2}−2 at 800~mK. We study electronic inelastic processes in Th (3^33P0_00​) and find no quenching even after 10610^6106 collisions at 800~mK. We measure the vibrational quenching cross section for ThO~(X,~nu=1\\nu=1nu=1) to be (7.9pm2.7)times10−19(7.9 \\pm 2.7) \\times 10^{-19}(7.9pm2.7)times10−19~cm−2^{-2}−2 at 800~mK. Finally, we observe indirect evidence for ThO (X, nu=0\\nu=0nu=0)--3^33He van der Waals complex formation, and measure the 3-body recombination rate constant to be Gamma3=(8pm2)times10−33\\Gamma_3 = (8 \\pm 2) \\times 10^{-33}Gamma3​=(8pm2)times10−33~cm6^66s−1^{-1}−1 at 2.4~K. The stability of the ground Th (3^33F2_22​) state, metastable Th (3^33P0_00​) state, and vibrational excited ThO (X, nu=1\\nu=1nu=1) state provides data on anisotropic interactions in new systems and opens up the possibility for further studies and experiments, including trapping.
We measure the ratio $\ensuremath{\gamma}$ of the momentum transfer--to--vibrational quenching cross section for molecular thorium monoxide (ThO) [$X{(}^{1}{\ensuremath{\Sigma}}^{+})$, v=1v=1v=1, J=0J=0J=0] in collisions with atomic helium between 800 mK and 2.4 K. We find $\ensuremath{\gamma}\ensuremath{\sim}{10}^{4}$. We also observe indirect evidence for ThO-He van der Waals complex formation, which has been predicted by theory [Tscherbul, Sayfutyarova, Buchachenko, and Dalgarno, J. Chem. Phys. 134, 144301 (2011)], and in conjunction, we determine the three-body recombination rate constant at 2.4 K, ${\ensuremath{\Gamma}}_{3}=8\ifmmode\pm\else\textpm\fi{}2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}33}$ cm6{\mathrm{cm}}^{6}cm6 ${\mathrm{s}}^{\ensuremath{-}1}$.
We measure the ratio γ of the momentum transfer–to–vibrational quenching cross section for molecular thorium monoxide (ThO) [X([superscript 1]Σ[superscript +]), v = 1, J = 0] in collisions with atomic helium between 800 mK and 2.4 K. We find γ ∼ 10[superscript 4]. We also observe indirect evidence for ThO-He van der Waals complex formation, which has been predicted by theory [Tscherbul, Sayfutyarova, Buchachenko, and Dalgarno, J. Chem. Phys. 134, 144301 (2011)], and in conjunction, we determine the three-body recombination rate constant at 2.4 K, Γ[subscript 3] = 8 ± 2 × 10[superscript −33] cm[superscript 6] s[superscript −1].
The cross section for the transfer of excitation from the 23P02^{3}P_{0}23P0​ level of helium to the 23P12^{3}P_{1}23P1​ and 23P22^{3}P_{2}23P2​ levels as a result of collisions with the ground-state helium atom (11S01^{1}S_{0}11S0​) has been measured with a conventional resonance-fluorescence technique. A He4{\mathrm{He}}^{4}He4 source excited the $2^{3}S_{1}\ensuremath{-}2^{3}P_{0}$ transition in a He3{\mathrm{He}}^{3}He3 absorption cell. The scattered light was examined with a high-resolution grating spectrometer and the ratio of the $2^{3}P_{0}\ensuremath{\rightarrow}2^{3}S_{1}$ to the $2^{3}P_{1,2}\ensuremath{\rightarrow}2^{3}S_{1}$ intensities was measured as a function of cell pressure from 0.05 to 10 Torr. The cross section for collision-induced transitions out of the 23P02^{3}P_{0}23P0​ level is found to be (68\ifmmode\pm\else\textpm\fi{}3) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}16}$ cm2{\mathrm{cm}}^{2}cm2 at room temperature.
Absolute velocity-resolved total integral cross sections have been measured for collisions of helium singlet (2 1 S 0 ) and triplet (2 3 S 1 2) metastable (He*) atoms with ground-state helium, neon, and argon atoms in the thermal velocity range of 1.0-3.5*10 5 cm s -1 . Additional measurements on the He*-Ne system with a large input aperture at the detector to suppress the sensitivity of the apparatus to elastic scattering failed to show the previously predicted (Arathoon) sharply rising velocity structure in the inelastic excitation transfer cross sections.