Abstract

Scattering of a quantum particle with internal structure is fundamentally different from that of a point particle and shows quantum effects such as the modification of transmission due to tunnelling and trapping of the particle. As in a preceding paper (Shore et al 2014 New J. Phys. 17 013046) we consider a model of a symmetric, rigid rotor travelling through an aperture in a thin but impenetrable screen which is perpendicular to both the direction of motion and the rotation axis. We determine the quantum mechanical properties of this two-dimensional geometrical model using a quasi one-dimensional scattering problem with unconventional boundaries. Our calculations rely on finding the Green's function, which has a direct connection to the scattering matrix. Evaluated on a discrete lattice the Hamiltonian is ‘dressed’ by a self-energy correction that takes into account the open boundary conditions in an exact way. We find that the passage through the aperture can be suppressed or enhanced as a result of the rotational motion. These effects manifest themselves through resonances in the transmission probability as a function of incident energy and symmetry of the incident wavefunction. We determine the density-of-states to reveal the mode structure of resonant states and to exhibit the lifetimes of temporary trapping within the aperture.

Highlights

  • In a previous article [1], referred hereafter as article I, we have considered the motion of a structured particle, idealized as a symmetric rigid rotor, passing through an aperture whose size is comparable to the particle

  • In order to bring out the similarities and differences between classical and quantum mechanical scattering, we consider an ensemble of non-rotating classical particles far away from the aperture, all with fixed initial energy ε and with an orientation angle φ distributed evenly on the interval −π 2 ⩽ φ ⩽ π 2

  • The calculations were carried out by a numerical method based on the Greens function of the problem in a discrete lattice representation

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Summary

13 February 2015

Physics and Astronomy, Texas A&M University, College Station, TX 77843-4242, USA 5 Author to whom any correspondence should be addressed.

Introduction
The model: a symmetric rigid rotor constrained to a track
Classical transmission probability
The quantum mechanical scattering problem
Greens function in the box
The wavefunction in the box
Numerical results
Conclusions

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