– 29 – 5.2.1. Photoevaporation According to photoevaporation models (e.g., Alexander et al. 2006), extreme UV photons, originating in the stellar chromosphere, ionize and heat the circumstellar hydrogen. Beyond some critical radius, the thermal velocity of the ionized hydrogen exceeds its escape velocity and the material is lost as a wind. At early stages in the evolution of the disk, the accretion rate across the disk dominates over the evaporation rate, and the disk undergoes standard viscous evolution. Later on, as the accretion rate drops to the level of the photoevaporation rate, the outer disk is no longer able to resupply the inner disk with material, the inner disk drains on a viscous timescale, and an inner hole is formed. Once an inner hole has formed, the entire disk dissipates very rapidly from the inside out as a consequence of the direct irradiation of the disk’s inner edge. Thus, transition disks created by photoevaporation are expected to have relatively low masses (M$_{DISK}$ < 5 M$_{JUP}$ ) and negligible accretion ( < 10 − 10 M$_{⊙}$yr − $^{1}$). We find that 9 of our 26 transition disks have low disk mass ( < 0.6-2.5 M$_{JUP}$ ) and negligible accretion (M$_{acc}$ < 10 − 11 M$_{⊙}$/year) and are hence consistent with photoevaporation. The SEDs of these objects are shown in Figure 9. These objects appear all in the lower left corner of Figure 6, which shows the disk mass as a function of accretion rate for our sample. However, they occupy different regions of the α$_{excess}$ vs λ$_{turn}$$_{−}$$_{off}$ parameter space. The majority of these objects have α$_{excess}$ ≲ -1, the typical value of CTTS with “full disks” (see Figure 10). These objects are therefore consistent with relatively flat, radially continuous disks. Two objects, targets # 5 and 19, have α$_{excess}$ ≳ 0, and are thus suggestive of sharp inner holes. Target #12 also has an steep SED, but between 24 and 70 µ m, suggesting a larger inner hole $^{12}$. Sharp inner holes could also arise from dynamical interactions between $^{12}$The mid-IR excess of target #12 (DoAr 21) comes from heated material that is at least 100 AU away from the star and it has been suggested it may originate from a small-scale