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Physical Review Letters

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

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

Published Sep 1, 2014• 1 citation
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Abstract

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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Vibrational quenching of the electronic ground state in ThO in cold collisions with He3

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We measure the ratio $\ensuremath{\gamma}$ of the momentum transfer--to--vibrational quenching cross section for molecular thorium monoxide (ThO) [$X{(}^{1}{\ensuremath{\Sigma}}^{+})$, $v=1$, $J=0$] 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, ${\ensuremath{\Gamma}}_{3}=8\ifmmode\pm\else\textpm\fi{}2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}33}$ ${\mathrm{cm}}^{6}$ ${\mathrm{s}}^{\ensuremath{-}1}$.

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Inelastic collisions of atomic thorium and molecular thorium monoxide with cold helium-3

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We measure inelastic cross sections for atomic thorium (Th) and molecular thorium monoxide (ThO) in collisions with $^3$He at temperatures near 1 K. We determine the Zeeman relaxation cross section for Th ($^3$F$_2$) to be $\\sim 2 \\times 10^{-17}$~cm$^{-2}$ at 800~mK. We study electronic inelastic processes in Th ($^3$P$_0$) and find no quenching even after $10^6$ collisions at 800~mK. We measure the vibrational quenching cross section for ThO~(X,~$\\nu=1$) to be $(7.9 \\pm 2.7) \\times 10^{-19}$~cm$^{-2}$ at 800~mK. Finally, we observe indirect evidence for ThO (X, $\\nu=0$)--$^3$He van der Waals complex formation, and measure the 3-body recombination rate constant to be $\\Gamma_3 = (8 \\pm 2) \\times 10^{-33}$~cm$^6$s$^{-1}$ at 2.4~K. The stability of the ground Th ($^3$F$_2$) state, metastable Th ($^3$P$_0$) state, and vibrational excited ThO (X, $\\nu=1$) state provides data on anisotropic interactions in new systems and opens up the possibility for further studies and experiments, including trapping.

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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

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

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Interactions and dynamics of metastable triplet-state helium dimer with Ne and Ar

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arXiv:2609.34713•Sep 28, 2026•0 citations

A Cryogenic Beam of Refractory, Chemically Reactive Molecules with Expansion Cooling

David P. DeMille, Nicholas R. Hutzler, Maxwell F. Parsons +7 more

Cryogenically cooled buffer gas beam sources of the molecule thorium monoxide (ThO) are optimized and characterized. Both helium and neon buffer gas sources are shown to produce ThO beams with high flux, low divergence, low forward velocity, and cold internal temperature for a variety of stagnation densities and nozzle diameters. The beam operates with a buffer gas stagnation density of \\(\\sim 10^{15}-10^{16}\\) cm\\(^{-3}\\) (Reynolds number \\(\\sim 1-100\\)), resulting in expansion cooling of the internal temperature of the ThO to as low as 2 K. For the neon (helium) based source, this represents cooling by a factor of about 10 (2) from the initial nozzle temperature of about 20 K (4 K). These sources deliver \\(\\sim 10^{11}\\) ThO molecules in a single quantum state within a 1-3 ms long pulse at 10 Hz repetition rate. Under conditions optimized for a future precision spectroscopy application [A C Vutha et al 2010 J. Phys. B: At. Mol. Opt. Phys. 43 074007], the neon-based beam has the following characteristics: forward velocity of 170 m/s, internal temperature of 3.4 K, and brightness of \\(3 \\times 10^{11}\\) ground state molecules per steradian per pulse. Compared to typical supersonic sources, the relatively low stagnation density of this source, and the fact that the cooling mechanism relies only on collisions with an inert buffer gas, make it widely applicable to many atomic and molecular species, including those which are chemically reactive, such as ThO.

•Jan 1, 2011•34 citations
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 ${\mathrm{s}}^{\ensuremath{-}1}$.
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.
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.
Helium dimer in its metastable triplet electronic state, He2(a 3Σu+)_2(a~^3Σ_u^+)2​(a 3Σu+​), is a promising candidate for direct laser cooling and precision measurements. Interactions and collisions involving He2(a 3Σu+)_2(a~^3Σ_u^+)2​(a 3Σu+​) remain unexplored in ultracold and cold energy domains. Here, we present the first theoretical investigation of intermolecular interactions and collision dynamics of He2(a 3Σu+)_2(a~^3Σ_u^+)2​(a 3Σu+​)+Ne van der Waals complex. For the ground electronic state, X 3A′X~^3\mathrm{A}'X 3A′, we employ a spin-restricted coupled cluster method with single, double, and noniterative triple excitations. The resulting interaction potential exhibits an extremely shallow well with a depth of 4.612 cm−1^{-1}−1. We construct a three-dimensional vibrationally averaged potential energy surface. Using this surface, we perform full close-coupling calculations including fine-structure levels of He2(a 3Σu+)_2(a~^3Σ_u^+)2​(a 3Σu+​) to investigate collisional excitation and quenching induced by Ne. We analyze the low-energy scattering dynamics and model resonant features associated with quasi-bound states supported by interaction potential. Propensity rule for fine-structure conserving transitions is established. We additionally consider He2_22​+Ar collisions and compare their energy dependence and resonance structure with those of He2_22​+Ne. The He2_22​+Ar system exhibits a richer resonance structure, highlighting the sensitivity of low-energy scattering to interaction potential and reduced mass. Calculated PES and scattering properties provide a reliable benchmark for description of He2_22​+Ne van der Waals complex and may be useful for interpretation of future experimental spectra and collision measurements.
Cryogenically cooled buffer gas beam sources of the molecule thorium monoxide (ThO) are optimized and characterized. Both helium and neon buffer gas sources are shown to produce ThO beams with high flux, low divergence, low forward velocity, and cold internal temperature for a variety of stagnation densities and nozzle diameters. The beam operates with a buffer gas stagnation density of \\(\\sim 10^{15}-10^{16}\\) cm\\(^{-3}\\) (Reynolds number \\(\\sim 1-100\\)), resulting in expansion cooling of the internal temperature of the ThO to as low as 2 K. For the neon (helium) based source, this represents cooling by a factor of about 10 (2) from the initial nozzle temperature of about 20 K (4 K). These sources deliver \\(\\sim 10^{11}\\) ThO molecules in a single quantum state within a 1-3 ms long pulse at 10 Hz repetition rate. Under conditions optimized for a future precision spectroscopy application [A C Vutha et al 2010 J. Phys. B: At. Mol. Opt. Phys. 43 074007], the neon-based beam has the following characteristics: forward velocity of 170 m/s, internal temperature of 3.4 K, and brightness of \\(3 \\times 10^{11}\\) ground state molecules per steradian per pulse. Compared to typical supersonic sources, the relatively low stagnation density of this source, and the fact that the cooling mechanism relies only on collisions with an inert buffer gas, make it widely applicable to many atomic and molecular species, including those which are chemically reactive, such as ThO.