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The surface of diamond is reported to undergo nonablative photochemical etching when exposed to ultraviolet (UV) radiation which allows controlled single and partial layer removal of lattice layers. Oxygen termination of surface dangling bonds is known to be crucial for the etching process; however, the exact mechanism of carbon ejection remains unclear. We investigate the interaction of UV laser pulses with oxygen-terminated diamond surfaces using atomic-scale surface characterization combined with first- principles time-dependent density functional theory calculations. We present evidence for laser-induced desorption (LID) from carbonyl functional groups at the diamond f001g surface. The doubly bonded carbonyl group is photoexcited into a triply bonded CO-like state, including scission of the underlying C─C bonds. The carbon removal process in LID is atom by atom; therefore, this mechanism provides a novel “top-down” approach for creating nanostructures on the surface of diamond and other carbon- containing semiconductors.