Snapshots of the outgoing wave packets at <em>t</em> = 3.4 μs

<p><strong>Figure 2.</strong> Snapshots of the outgoing wave packets at <em>t</em> = 3.4 μs. Coordinate (in linear scale) and momentum distribution (in semilogarithmic scale) for a particle reflected on the oscillating surface (amplitude <em>d</em> = 4 nm) for different frequencies ω and fixed <em>x</em>₀ = 4 <b>×</b> 10⁻¹⁰ m (black curves). Red dashed lines: corresponding distributions for the static potential.</p> <p><strong>Abstract</strong></p> <p>We describe an experimentally realistic situation of the quantum reflection of helium atoms from an oscillating surface. The temporal modulation of the potential induces clear sidebands in the reflection probability as a function of momentum. These sidebands could be exploited to slow down atoms and molecules in the experiment.