Based on the recently determined Rydberg series of the
3 
excimer states of Ne*
2, Ar*
2and Kr*
2, the photoionization cross sections of these molecules are calculated using a single-channel quantum defect method. These cross sections are found to differ considerably from those of the asymptotic metastable atomic Rg*(

) states, but are in good agreement with recently reported experiments at isolated wavelengths. The implications of these results for VUV and XUV lasers are discussed.