Incident electrons follow a parabolic trajectory when an electric field is applied normal to the surface of a metal crystal with force vector directed outwards. Under appropriate conditions touching trajectories may be neglected, and electron-surface-plasmon scattering is dominated by trajectories with closest approach distance. Experimental results are presented for Mo indicating that only the 1.3-eV molybdenum surface plasmon is excited. Application of this new technique to measurements such as surface-plasmon dispersion is outlined.

• Received 8 November 1976

DOI:https://doi.org/10.1103/PhysRevLett.38.36