Photoionisation spectra for krypton and argon were measured as a function of pressure (p<or=230 Torr) for photon energies below and above the first atomic ionisation limit I_g. The photocurrent spectrum below I_g evolves, with increasing pressure, from peaks at the energies of the atomic transitions, into broad overlapping bands. The upper limit for the photoresponse renders a (pressure-independent) yield function for ionisation with onsets at 12.84 and 14.49 eV for krypton and argon, respectively. The results are interpreted in terms of a simple statistical model for the decay of the Rydberg state, with energies above the onset, into a dimer-ion-electron pair.