Figure 3

Level scheme for ionisation of neon by the fundamental and its second harmonic (a) and helium by the fundamental and its third harmonic (b,c). The (short) red arrows mark the fundamental photon, while the (long) blue ones indicate the higher harmonic. The horizontal lines show the levels for photoabsorption and autoionisation processes. The relevant energy levels (not to scale) are given on the side of the respective frames.