We demonstrate an approach for producing a high flux beam of
7Li
4He dimers by performing post-nozzle seeding of a lithium beam into a supersonic helium expansion. The molecular beam has a longitudinal temperature of 13(6) mK and a continuous flux on the order of
1011 dimers/s. Monte Carlo simulations of molecular formation based on ab-initio quantum scattering calculations are carried out and compared to the experimentally observed molecular flux. Extensions of this work could lead towards a more quantitative understanding of few-body collision processes of alkali and helium atoms.
We present three-dimensional Monte Carlo simulations of the capture of 1000 K
7Li or 500 K
87Rb atoms by a continuous supersonic
4He jet and show that intense, cold alkali-metal beams form. The simulations use differential cross sections obtained from quantum scattering calculations of
7Li or
87Rb atoms with
4He atoms for relative collision energies between $k\ifmmode\times\else\texttimes\fi{}1$ mK and $k\ifmmode\times\else\texttimes\fi{}3000$ K, where
k is the Boltzmann constant. For collision energies higher than approximately $k\ifmmode\times\else\texttimes\fi{}4$ K the collisions favor forward scattering, deflecting the
7Li or
87Rb atoms by no more than a few degrees. From the simulations, we find that about 1% of the lithium atoms are seeded into the
4He jet, resulting in a lithium beam with a most probable velocity of about
210m/s and number densities on the order of ${10}^{8}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$. Simulations predict narrow yet asymmetric velocity distributions which are verified by comparing to fluorescence measurements of the seeded
7Li atoms. We find agreement between simulated and experimentally measured seeded
7Li densities to be better than 50% across a range of
4He flow rates. We make predictions for seeding efficiency and cooling of
87Rb by a supersonic
4He jet. The seeding efficiency for
87Rb is expected to be similar to
7Li.
The authors demonstrate an intense, continuous cold atomic beam generated via postnozzle seeding of a supersonic
4He jet with
7Li atoms, which is comparable to the highest flux sources based on laser cooling. The technique could potentially be widely applicable to any paramagnetic atom or molecule.
We demonstrate an approach for producing a high-flux beam of
7Li4He dimers by performing postnozzle seeding of a lithium beam into a supersonic helium expansion. The molecular beam has a longitudinal temperature of 13(6) mK and a continuous flux on the order of
1011 dimers/s confined within a solid angle of 0.16 sr. Monte Carlo simulations of molecular formation based on
ab initio quantum scattering calculations are carried out and compared to the experimentally observed molecular flux. Extensions of this work could lead towards a more quantitative understanding of few-body collision processes of alkali and helium atoms.
Abstract Well-collimated, high-intensity beams of neutral atoms have many applications ranging from atom microscopy to atom interferometry to ultracold atomic physics. We experimentally demonstrate a method for brightening a supersonic atomic beam and observe an increase in the phase space density by a factor of at least 20. Our scheme relies upon a permanent magnetic hexapole lens to focus a divergent beam of neutral atoms emitted from a supersonic nozzle and transverse laser cooling as the beam converges downstream from the lens so as to create a dense, narrow, Doppler-collimated atomic beam. In principle, this method can be repeated multiple times in series for further beam brightening.