Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:2209.06564 · Molecular Physics

Cryogenic buffer gas beams of AlF, CaF, MgF, YbF, Al, Ca, Yb and NO – a comparison

Sidney C. Wright, Maximilian Doppelbauer, Simon Hofsäss, H. Christian Schewe, Boris G. Sartakov, Gerard Meijer, Stefan Truppe

Published Nov 26, 2022• 29 citations
arXivHTMLPDF

Abstract

Cryogenic buffer gas beams are central to many cold molecule experiments. Here, we use absorption and fluorescence spectroscopy to directly compare molecular beams of AlF, CaF, MgF and YbF molecules, produced by chemical reaction of laser ablated atoms with fluorine rich reagents. The beam brightness for AlF is measured as 2×1012 molecules per steradian per pulse in a single rotational state, comparable to an Al atomic beam produced in the same setup. The CaF, MgF and YbF beams show an order of magnitude lower brightness than AlF and far below the brightness of Ca and Yb beams. The addition of either NF3 or SF6 to the cell extinguishes the Al atomic beam, but has a minimal effect on the Ca and Yb beams. NF3 reacts more efficiently than SF6, as a significantly lower flow rate is required to maximise the molecule production, which is particularly beneficial for long-term stability of the AlF beam. We use NO as a proxy for the reactant gas as it can be optically detected. We demonstrate that a cold, rotationally pure NO beam can be generated by laser desorption, thereby gaining insight into the dynamics of the reactant gas inside the buffer gas cell.

DOI
10.1080/00268976.2022.2146541

Related papers

Buffer gas cooling of YbF molecules

Sarah M. Skoff

This thesis reports on the production and characterisation of the first slow and cold beam of YbF molecules using buffer gas cooling. These molecules are being used to measure the electron’s electric dipole moment, and an intense source of slow-moving molecules is desirable for this experiment. The molecules are loaded into a buffer gas cell via laser ablation where they thermalise with cold helium buffer gas. They are then detected inside the cell using laser absorption imaging and spectroscopy on the X2Σ+→A2II1/2 transition. The formation, diffusion and thermalisation dynamics of the molecules inside the cell are studied. Measurements of laser absorption versus intensity reveal that saturation of the absorption is due to a competition between optical pumping into dark states and repopulation of the addressed level by inelastic and velocity-changing collisions. A beam of YbF molecules is extracted through an aperture in the buffer gas cell and characterised using laser induced fluorescence detection. Peak fluxes of 1010 molecules per steradian per pulse, in the rotational and vibrational ground state, are obtained. The translational and rotational temperatures are in equilibrium with the cell temperature of 4 K. The forward velocity of the pulses can be varied between 130 m/s and 200 m/s by changing the buffer gas pressure. This source is an order of magnitude brighter and more than three times slower than a supersonic source of YbF molecules and provides an excellent starting point for improving the measurement of the electron’s electric dipole moment and for deceleration and trapping experiments. In order to reduce the helium load on the vacuum system and to shorten the molecular pulses, a second set-up, delivering the buffer gas into an open copper cylinder in pulses rather than in a continuous flow,is characterised and shows promising first results.

•Sep 1, 2011•2 citations

Chemistry in a Cryogenic Buffer Gas Cell

Qi Sun, Jinyu Dai, Rian Koots +4 more

Cryogenic buffer gas sources are ubiquitous for producing cold, collimated molecular beams for quantum science, chemistry, and precision measurements. The molecules are typically produced by laser ablating a metal target in the presence of a donor gas. The radical of interest emerges due to a barrier-free reaction or under thermal or optical excitation. High-barrier reactions, such as between Ca and H 2, should be precluded. We study chemical reactions between Ca and three hydrogen isotopologues (H 2, D 2, and HD) in a cryogenic cell with helium buffer gas. We observe that H 2 can serve as both a reactant and a buffer gas, outperforming D 2 and HD. We use a reaction network model to describe the chemical dynamics and find that the enhanced molecular yield can be attributed to rapid vibrational excitations of the reactant gas. Our results demonstrate a robust method for generating bright cold beams of alkaline-earth-metal hydrides for laser cooling and trapping.

arXiv:2501.05613•The Journal of Physical Chemistry Letters•Dec 26, 2025•2 citations

Continuous thermochemical sources of AlF molecules

P. Kukreja, Priyansh Agarwal, Maximilian Doppelbauer +10 more

The AlF molecule, currently subject to laser cooling and trapping efforts, has the advantage that it can be efficiently produced in a thermochemical reaction between sublimated aluminum trifluoride and aluminum metal. Here we present a series of experiments with continuous molecular beam sources of AlF, utilising this reaction. We demonstrate a compact AlF molecular beam oven whose total far-field brightness is $5\times 10^{15}$ molecules per steradian per second at 923~K, just below the melting temperature of aluminum metal. The continuous output from the oven begins to exceed the peak brightness of a jet-cooled, ablation-based supersonic AlF source for the $v=0$, $J=7$ level, and we obtain an excellent signal-to-noise ratio with the oven in pulsed laser ionisation spectroscopy experiments. By delivering flux from the oven into a cryogenic Ne buffer gas cell, we lower the rotational temperature of the beam to around 30~K and reduce its most probable forward velocity from 600~ms$^{-1}$ to 200~ms$^{-1}$. In addition, we demonstrate that AlF can be made in a simple dispenser package, and observe that molecules thermalise to the laboratory temperature after colliding with vacuum chamber walls of the experiment. The resulting transient AlF vapour may enable direct loading of a molecular magneto-optical trap.

arXiv:2604.04509•Apr 6, 2026•0 citations

Slow molecular beams from a cryogenic buffer gas source

A. D. White, S. Popa, Jorge Mellado Muñoz +4 more

We study the properties of a cryogenic buffer gas source that uses a low-temperature two-stage buffer gas cell to produce very slow beams of ytterbium monofluoride molecules. The molecules are produced by laser ablation inside the cell and extracted into a beam by a flow of cold helium. We measure the flux and velocity distribution of the beam as a function of ablation energy, helium flow rate, cell temperature, and the size of the gap between the first and second stages of the cell. We also compare the velocity distributions from one-stage and two-stage cells. The one-stage cell emits a beam with a speed of about 82 m s − 1 and a translational temperature of 0.63 K. The slowest beams are obtained using the two-stage cell at the lowest achievable cell temperature of 1.8 K. This beam has a peak velocity of 56 m s − 1 and a flux of 9 × 10 9 ground-state molecules per steradian per pulse, with a substantial fraction at speeds below 40 m s − 1 . These slow molecules can be decelerated further by radiation pressure slowing and then captured in a magneto-optical trap. Published by the American Physical Society 2024

arXiv:2408.01862•Physical Review Research•Dec 3, 2024•7 citations

A buffer gas beam source for short, intense and slow molecular pulses

Stefan Truppe, M. Hambach, Sarah M. Skoff +6 more

Experiments with cold molecules usually begin with a molecular source. We describe the construction and characteristics of a cryogenic buffer gas source of CaF molecules. The source emits pulses with a typical duration of 240 μs, a mean speed of about 150 m/s, and a flux of 5×1010 molecules per steradian per pulse in a single rotational state.

arXiv:1707.06291•Journal of Modern Optics•Nov 5, 2017•68 citations

Continuous thermochemical sources of AlF molecules

P. Kukreja, Priyansh Agarwal, Maximilian Doppelbauer +10 more

Abstract The AlF molecule, currently subject to laser cooling and trapping efforts, has the advantage that it can be efficiently produced in a thermochemical reaction between sublimated aluminum trifluoride and aluminum metal. Here we present a series of experiments with continuous molecular beam sources of AlF, utilizing this reaction. We demonstrate a compact AlF molecular beam oven whose total far-field brightness is 5 × 10 15 molecules per steradian per second at 923 K, just below the melting temperature of aluminum metal. The continuous output from the oven begins to exceed the peak brightness of a jet-cooled, ablation-based supersonic AlF source for the v = 0 , J = 7 level, and we obtain an excellent signal-to-noise ratio with the oven in pulsed laser ionization spectroscopy experiments. By delivering flux from the oven into a cryogenic Ne buffer gas cell, we lower the rotational temperature of the beam to around 30 K and reduce its most probable forward velocity from 600 m s − 1 to 200 m s − 1 . In addition, we demonstrate that AlF can be made in a simple dispenser package, and observe that molecules thermalize to the laboratory temperature after colliding with vacuum chamber walls of the experiment. The resulting transient AlF vapor may enable direct loading of a molecular magneto-optical trap.

New Journal of Physics•May 19, 2026•0 citations
Cryogenic buffer gas beams are central to many cold molecule experiments. Here, we use absorption and fluorescence spectroscopy to directly compare molecular beams of AlF, CaF, MgF and YbF molecules, produced by chemical reaction of laser ablated atoms with fluorine rich reagents. The beam brightness for AlF is measured as 2×1012 molecules per steradian per pulse in a single rotational state, comparable to an Al atomic beam produced in the same setup. The CaF, MgF and YbF beams show an order of magnitude lower brightness than AlF and far below the brightness of Ca and Yb beams. The addition of either NF3 or SF6 to the cell extinguishes the Al atomic beam, but has a minimal effect on the Ca and Yb beams. NF3 reacts more efficiently than SF6, as a significantly lower flow rate is required to maximise the molecule production, which is particularly beneficial for long-term stability of the AlF beam. We use NO as a proxy for the reactant gas as it can be optically detected. We demonstrate that a cold, rotationally pure NO beam can be generated by laser desorption, thereby gaining insight into the dynamics of the reactant gas inside the buffer gas cell.
This thesis reports on the production and characterisation of the first slow and cold beam of YbF molecules using buffer gas cooling. These molecules are being used to measure the electron’s electric dipole moment, and an intense source of slow-moving molecules is desirable for this experiment. The molecules are loaded into a buffer gas cell via laser ablation where they thermalise with cold helium buffer gas. They are then detected inside the cell using laser absorption imaging and spectroscopy on the X2Σ+→A2II1/2 transition. The formation, diffusion and thermalisation dynamics of the molecules inside the cell are studied. Measurements of laser absorption versus intensity reveal that saturation of the absorption is due to a competition between optical pumping into dark states and repopulation of the addressed level by inelastic and velocity-changing collisions. A beam of YbF molecules is extracted through an aperture in the buffer gas cell and characterised using laser induced fluorescence detection. Peak fluxes of 1010 molecules per steradian per pulse, in the rotational and vibrational ground state, are obtained. The translational and rotational temperatures are in equilibrium with the cell temperature of 4 K. The forward velocity of the pulses can be varied between 130 m/s and 200 m/s by changing the buffer gas pressure. This source is an order of magnitude brighter and more than three times slower than a supersonic source of YbF molecules and provides an excellent starting point for improving the measurement of the electron’s electric dipole moment and for deceleration and trapping experiments. In order to reduce the helium load on the vacuum system and to shorten the molecular pulses, a second set-up, delivering the buffer gas into an open copper cylinder in pulses rather than in a continuous flow,is characterised and shows promising first results.
Cryogenic buffer gas sources are ubiquitous for producing cold, collimated molecular beams for quantum science, chemistry, and precision measurements. The molecules are typically produced by laser ablating a metal target in the presence of a donor gas. The radical of interest emerges due to a barrier-free reaction or under thermal or optical excitation. High-barrier reactions, such as between Ca and H 2, should be precluded. We study chemical reactions between Ca and three hydrogen isotopologues (H 2, D 2, and HD) in a cryogenic cell with helium buffer gas. We observe that H 2 can serve as both a reactant and a buffer gas, outperforming D 2 and HD. We use a reaction network model to describe the chemical dynamics and find that the enhanced molecular yield can be attributed to rapid vibrational excitations of the reactant gas. Our results demonstrate a robust method for generating bright cold beams of alkaline-earth-metal hydrides for laser cooling and trapping.
The AlF molecule, currently subject to laser cooling and trapping efforts, has the advantage that it can be efficiently produced in a thermochemical reaction between sublimated aluminum trifluoride and aluminum metal. Here we present a series of experiments with continuous molecular beam sources of AlF, utilising this reaction. We demonstrate a compact AlF molecular beam oven whose total far-field brightness is 5×10155\times 10^{15}5×1015 molecules per steradian per second at 923~K, just below the melting temperature of aluminum metal. The continuous output from the oven begins to exceed the peak brightness of a jet-cooled, ablation-based supersonic AlF source for the v=0v=0v=0, J=7J=7J=7 level, and we obtain an excellent signal-to-noise ratio with the oven in pulsed laser ionisation spectroscopy experiments. By delivering flux from the oven into a cryogenic Ne buffer gas cell, we lower the rotational temperature of the beam to around 30~K and reduce its most probable forward velocity from 600~ms−1^{-1}−1 to 200~ms−1^{-1}−1. In addition, we demonstrate that AlF can be made in a simple dispenser package, and observe that molecules thermalise to the laboratory temperature after colliding with vacuum chamber walls of the experiment. The resulting transient AlF vapour may enable direct loading of a molecular magneto-optical trap.
We study the properties of a cryogenic buffer gas source that uses a low-temperature two-stage buffer gas cell to produce very slow beams of ytterbium monofluoride molecules. The molecules are produced by laser ablation inside the cell and extracted into a beam by a flow of cold helium. We measure the flux and velocity distribution of the beam as a function of ablation energy, helium flow rate, cell temperature, and the size of the gap between the first and second stages of the cell. We also compare the velocity distributions from one-stage and two-stage cells. The one-stage cell emits a beam with a speed of about 82 m s − 1 and a translational temperature of 0.63 K. The slowest beams are obtained using the two-stage cell at the lowest achievable cell temperature of 1.8 K. This beam has a peak velocity of 56 m s − 1 and a flux of 9 × 10 9 ground-state molecules per steradian per pulse, with a substantial fraction at speeds below 40 m s − 1 . These slow molecules can be decelerated further by radiation pressure slowing and then captured in a magneto-optical trap. Published by the American Physical Society 2024
Abstract The AlF molecule, currently subject to laser cooling and trapping efforts, has the advantage that it can be efficiently produced in a thermochemical reaction between sublimated aluminum trifluoride and aluminum metal. Here we present a series of experiments with continuous molecular beam sources of AlF, utilizing this reaction. We demonstrate a compact AlF molecular beam oven whose total far-field brightness is 5 × 10 15 molecules per steradian per second at 923 K, just below the melting temperature of aluminum metal. The continuous output from the oven begins to exceed the peak brightness of a jet-cooled, ablation-based supersonic AlF source for the v = 0 , J = 7 level, and we obtain an excellent signal-to-noise ratio with the oven in pulsed laser ionization spectroscopy experiments. By delivering flux from the oven into a cryogenic Ne buffer gas cell, we lower the rotational temperature of the beam to around 30 K and reduce its most probable forward velocity from 600 m s − 1 to 200 m s − 1 . In addition, we demonstrate that AlF can be made in a simple dispenser package, and observe that molecules thermalize to the laboratory temperature after colliding with vacuum chamber walls of the experiment. The resulting transient AlF vapor may enable direct loading of a molecular magneto-optical trap.