Collisionless absorption in sharp-edged plasmas

The absorption of subpicosecond, obliquely incident laser light is studied using a 11/2D particle-in-cell code. Density scale lengths from L/{λ}=0.01 to 2 and laser irradiances between Iλ²=10¹⁴ and 10¹⁸ W cm^-2 {μ}m² are considered. ``Vacuum heating'' [F. Brunel, Phys. Rev. Lett. 59, 52 (1987)] dominates over resonance absorption for scale lengths L/{λ}0.1, and is most efficient when vosc/c{}3.1(L/{λ})². Absorbed energy is carried mainly by a ``superhot'' electron population with Uₕₒₜ{~}(Iλ²{)}1/3--1/2$.