Fig. 1. Pressure dependence of the average cluster size for He (dashed–dotted line), Ar (dashed line) and Xe (solid line) according to the Hagena scaling.

Fig. 2. The HHG spectrum from Ar at 14 bar backing pressure and intensity.

Fig. 3. Intensity dependence of the 15th harmonic for different gases at 6 bar backing pressure.

Fig. 4. Comparison of the pressure dependence of the 25th harmonic at intensity in He, Ar, and Xe.

Fig. 5. Intensity dependence of generation for Ar at 2, 6 and 12 bar backing pressure.

Fig. 6. Increasing blue shift of high harmonics with increasing intensity for 12 bar Ar backing pressure.

Fig. 7. Harmonic spectra from Xe at intensity for 2 and 12 bar (dotted line) backing pressure.

Fig. 8. Red shift of the 21st harmonic for Xe at intensity with increasing pressure.