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Physical Review Letters

Properties of the ground [superscript 3]F[subscript 2] state and the excited [superscript 3]P[subscript 0] state of atomic thorium in cold collisions with [superscript 3]He

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

Published Sep 1, 2014• 0 citations
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Abstract

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.

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Vibrational quenching of the electronic ground state in ThO in cold collisions with [superscript 3]He

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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].

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NH radicals are magnetically trapped and their Zeeman relaxation and energy transport collision cross sections with helium are measured. Continuous buffer-gas loading of the trap is direct from a room-temperature molecular beam. The Zeeman relaxation (inelastic) cross section of magnetically trapped electronic, vibrational, and rotational ground state NH molecules in collisions with $^{3}\mathrm{He}$ is measured to be $3.8\ifmmode\pm\else\textpm\fi{}1.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}19}\text{ }\text{ }{\mathrm{cm}}^{2}$ at 710 mK. The NH-He energy transport cross section is also measured, indicating a ratio of diffusive to inelastic cross sections of $\ensuremath{\gamma}=7\ifmmode\times\else\texttimes\fi{}{10}^{4}$, in agreement with recent theory [R. V. Krems, H. R. Sadeghpour, A. Dalgarno, D. Zgid, J. K\l{}os, and G. Cha\l{}asi\ifmmode \acute{n}\else \'{n}\fi{}ski, Phys. Rev. A 68, 051401 (2003)].

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New Journal of Physics•Jun 28, 2010•7 citations
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.
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 $\ensuremath{\gamma}\ensuremath{\sim}500$ 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 $\ensuremath{\tau}>130$ ms. The observed stability of Th[3P0{}^{3}{P}_{0}3P0​] 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 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].
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 ${\mathrm{s}}^{\ensuremath{-}1}$.
NH radicals are magnetically trapped and their Zeeman relaxation and energy transport collision cross sections with helium are measured. Continuous buffer-gas loading of the trap is direct from a room-temperature molecular beam. The Zeeman relaxation (inelastic) cross section of magnetically trapped electronic, vibrational, and rotational ground state NH molecules in collisions with 3He^{3}\mathrm{He}3He is measured to be $3.8\ifmmode\pm\else\textpm\fi{}1.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}19}\text{ }\text{ }{\mathrm{cm}}^{2}$ at 710 mK. The NH-He energy transport cross section is also measured, indicating a ratio of diffusive to inelastic cross sections of $\ensuremath{\gamma}=7\ifmmode\times\else\texttimes\fi{}{10}^{4}$, in agreement with recent theory [R. V. Krems, H. R. Sadeghpour, A. Dalgarno, D. Zgid, J. K\l{}os, and G. Cha\l{}asi\ifmmode \acute{n}\else \'{n}\fi{}ski, Phys. Rev. A 68, 051401 (2003)].