Molecules in the low temperature limit offer fascinating research perspectives in physics and chemistry, and molecule cooling and deceleration has developed into a research field of its own.The grand challenge today is to prepare dense samples with ample cold molecules.Towards this end, we present an elegant solution to this problem by a nonconventional approach, employing the centrifugal force in a rotating frame to decelerate molecules to a standstill.The centrifuge deceleration is a generic method since its principle is not associated with any specific internal structure of the molecules.Moreover, electrostatic guiding of molecules is applied throughout the deceleration process, which enables for the first time the deceleration of continuous molecular beams to achieve unprecedented high fluxes of slow molecules.In a proof-ofprinciple experiment, we demonstrate fluxes of ∼ 10 9 molecules/s and densities of ∼ 10 8 molecules/cm 3 below k B •1 K in the laboratory frame, originated from a roomtemperature effusive beam source.The efficiency of this decelerator is measured to be up to 20%, outperforming all the existing molecular deceleration methods.The generality of this method is demonstrated by the deceleration of several polyatomic molecular species, CH 3 F, CF 3 H, and CF 3 CCH.In addition to presenting the basic principle and the results, we also describe thoroughly in this thesis the design of the centrifuge decelerator, optimized through Monte-Carlo trajectory simulations, and the technical assembly.The second focus of this thesis is on the development and implementation of a simple and robust internal-state thermometry method for cold polyatomic molecules.The method is based on the combination of resonant radio-frequency depletion spectroscopy and Monte Carlo trajectory simulations.The radio-frequency depletion spectroscopy is capable of addressing 100% of the rotational states populated by the cold polyatomic molecules, as well as resolving their hyperfine states.With this tool, various aspects of cryogenic buffer-gas cooling used as a source of internally cold molecules are characterized.The properties of the cold molecular beams obtained at different buffer-gas temperature, densities, and cooling regimes, are analyzed.The cooling processes for different polyatomic molecules are compared.These studies reveal also two interesting phenomena in the buffer-gas cooling process.Firstly, evidence is provided that molecular rotational degrees of freedom can thermalize more efficiently than their translational ones.Secondly, the measurements provide indications for dependence of the collisional relaxation rate on the rotational states of the molecules.Molecules in the low temperature limit offer fascinating research perspectives in physics and chemistry, and molecule cooling and deceleration has developed into a research field of its own.The grand challenge today is to prepare dense samples with ample cold molecules.Towards this end, we present an elegant solution to this problem by a nonconventional approach, employing the centrifugal force in a rotating frame to decelerate molecules to a standstill.The centrifuge deceleration is a generic method since its principle is not associated with any specific internal structure of the molecules.Moreover, electrostatic guiding of molecules is applied throughout the deceleration process, which enables for the first time the deceleration of continuous molecular beams to achieve unprecedented high fluxes of slow molecules.In a proof-ofprinciple experiment, we demonstrate fluxes of ∼ 10 9 molecules/s and densities of ∼ 10 8 molecules/cm 3 below k B •1 K in the laboratory frame, originated from a roomtemperature effusive beam source.The efficiency of this decelerator is measured to be up to 20%, outperforming all the existing molecular deceleration methods.The generality of this method is demonstrated by the deceleration of several polyatomic molecular species, CH 3 F, CF 3 H, and CF 3 CCH.In addition to presenting the basic principle and the results, we also describe thoroughly in this thesis the design of the centrifuge decelerator, optimized through Monte-Carlo trajectory simulations, and the technical assembly.The second focus of this thesis is on the development and implementation of a simple and robust internal-state thermometry method for cold polyatomic molecules.The method is based on the combination of resonant radio-frequency depletion spectroscopy and Monte Carlo trajectory simulations.The radio-frequency depletion spectroscopy is capable of addressing 100% of the rotational states populated by the cold polyatomic molecules, as well as resolving their hyperfine states.With this tool, various aspects of cryogenic buffer-gas cooling used as a source of internally cold molecules are characterized.The properties of the cold molecular beams obtained at different buffer-gas temperature, densities, and cooling regimes, are analyzed.The cooling processes for different polyatomic molecules are compared.These studies reveal also two interesting phenomena in the buffer-gas cooling process.Firstly, evidence is provided that molecular rotational degrees of freedom can thermalize more efficiently than their translational ones.Secondly, the measurements provide indications for dependence of the collisional relaxation rate on the rotational states of the molecules.

Jan 1, 20171 citation

Control of cold molecular beams

Jochen Küpper

Jan 1, 20140 citations

Continuous Centrifuge Decelerator for Polar Molecules

Sotir Chervenkov, Xing Wu, Josef Bayerl +4 more

Producing large samples of slow molecules from thermal-velocity ensembles is a formidable challenge. Here we employ a centrifugal force to produce a continuous molecular beam with a high flux at near-zero velocities. We demonstrate deceleration of three electrically guided molecular species, ${\mathrm{CH}}_{3}\mathrm{F}$ , ${\mathrm{CF}}_{3}\mathrm{H}$ , and ${\mathrm{CF}}_{3}\mathrm{CCH}$ , with input velocities of up to $200\text{ }\text{ }{\mathrm{m}\text{ }\mathrm{s}}^{\ensuremath{-}1}$ to obtain beams with velocities below $15\text{ }\text{ }{\mathrm{m}\text{ }\mathrm{s}}^{\ensuremath{-}1}$ and intensities of several ${10}^{9}\text{ }\text{ }{\mathrm{mm}}^{\ensuremath{-}2}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$. The centrifuge decelerator is easy to operate and can, in principle, slow down any guidable particle. It has the potential to become a standard technique for continuous deceleration of molecules.Producing large samples of slow molecules from thermal-velocity ensembles is a formidable challenge. Here we employ a centrifugal force to produce a continuous molecular beam with a high flux at near-zero velocities. We demonstrate deceleration of three electrically guided molecular species, ${\mathrm{CH}}_{3}\mathrm{F}$, ${\mathrm{CF}}_{3}\mathrm{H}$, and ${\mathrm{CF}}_{3}\mathrm{CCH}$, with input velocities of up to $200\text{ }\text{ }{\mathrm{m}\text{ }\mathrm{s}}^{\ensuremath{-}1}$ to obtain beams with velocities below $15\text{ }\text{ }{\mathrm{m}\text{ }\mathrm{s}}^{\ensuremath{-}1}$ and intensities of several ${10}^{9}\text{ }\text{ }{\mathrm{mm}}^{\ensuremath{-}2}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$. The centrifuge decelerator is easy to operate and can, in principle, slow down any guidable particle. It has the potential to become a standard technique for continuous deceleration of molecules.

arXiv:1311.7119Physical Review LettersJan 6, 201481 citations

Cold and Slow Molecular Beam

Aug 17, 20160 citations

Preparation of Translationally Cold Neutral Molecules

Giulia Di Domenicantonio, Benjamin Bertsche, Andreas Osterwalder

Efforts at EPFL to obtain translationally cold neutral molecules are described. Active deceleration of polar molecules is performed by confining the molecules in moving three-dimensional electrostatic traps, and by appropriately choosing the velocity of those traps. Alternatively, cold molecules can be obtained by velocity filtering. Here, the velocity of the molecules is not changed, but instead the cold molecules are extracted from a thermal sample by using the competition between the electrostatic force and the centrifugal force inside a bent electrostatic guide for polar molecules.Efforts at EPFL to obtain translationally cold neutral molecules are described. Active deceleration of polar molecules is performed by confining the molecules in moving three-dimensional electrostatic traps, and by appropriately choosing the velocity of those traps. Alternatively, cold molecules can be obtained by velocity filtering. Here, the velocity of the molecules is not changed, but instead the cold molecules are extracted from a thermal sample by using the competition between the electrostatic force and the centrifugal force inside a bent electrostatic guide for polar molecules.

CHIMIA International Journal for ChemistrySep 30, 20113 citations

{\mathrm{CH}}_{3}\mathrm{F}

{\mathrm{CF}}_{3}\mathrm{H}

, and

{\mathrm{CF}}_{3}\mathrm{CCH}

, with input velocities of up to $200\text{ }\text{ }{\mathrm{m}\text{ }\mathrm{s}}^{\ensuremath{-}1}$ to obtain beams with velocities below $15\text{ }\text{ }{\mathrm{m}\text{ }\mathrm{s}}^{\ensuremath{-}1}$ and intensities of several ${10}^{9}\text{ }\text{ }{\mathrm{mm}}^{\ensuremath{-}2}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$. The centrifuge decelerator is easy to operate and can, in principle, slow down any guidable particle. It has the potential to become a standard technique for continuous deceleration of molecules.