Experiments with Supersonic Beams as a Source of Cold Atoms

Chapter 3
Slowing Supersonic Beams via Specular Reflection:
The Atomic Paddle
As experimental control of atomic motion has improved, the wave nature of
atomic beams has become an important factor in many experiments. Quantum me-
chanics states that like light, matter is both a particle and a wave. This has given
birth to a new class of experiments which exploit the wave nature of atoms and ma-
nipulate beams of atoms in a particle analog to optical manipulation of beams of
light. This growing field is known as atom optics, and much research has recently
gone into developing a toolbox for manipulating atomic beams.
Most of the work in atom optics has used laser cooled atoms [38, 39], which
provide several advantages. Since the atoms are laser cooled they are quite cold, and
beams can be produced at low velocities. This accentuates the wave nature of the
particles, as
λ = 2π
(3.1)
p
where λ is the de Broglie wavelength of a particle, and p is the particle’s momentum.
Furthermore, laser cooled atoms have an accessible transition an experimentalist can
use to both manipulate and detect the atoms in the beam. There are some drawbacks
to using laser cooled atoms however, most notably their sensitivity to stray fields.
It is rather difficult to effectively control the atomic motion of ground state
helium, due to the lack of accessible transitions with current laser technology. How-
ever, helium is known to reflect well from single crystal surfaces [40], which suggests
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