He atom scattering in the momentum space

Probability density functions (PDF) of He-W(112) scattering are in the momentum space.The incoming wave-packet has non-zero energy spread only in the the direction y. The energy spread - parallel to surface - is zero. The beam source is modeled as an ensemble of independent particle by an appropriate Gaussian wave-packet. x and y are parallel and perpendicular to the surface, respectively. px and py  in the direction x and y, respectively. Atomic units are used. Initial state: PDF is at the beam source. Final state: PDF is at the detector region. Between the initial and final states: PDF is propagating in the interaction region.

Further details can be found in:

"Resolution and transfer width of thermal energy atomic scattering from solid surfaces, G Varga, Applied Surface Science, 144-145 (1999) p. 64-68"
or
"Investigation of thermal energy atomic scattering from solid surfaces using 3D time-dependent Schrödinger equation, G. Varga, Surface Science, vol. 441 (1999) 472-478".