Photodesorption of NO from Au(100) using 3D surface-velocity map imaging.

We measured the fully resolved 3-dimensional velocity distributions of nitric oxide photodesorbed from a gold single crystal. These experiments combine time-of-flight measurements and the velocity map imaging technique to yield velocity distributions resolved in three dimensions for a prototypical surface-adsorbate system. Nitric oxide adsorbed on Au(100) was photodesorbed using a 355 nm laser beam. The desorbed NO molecules were ionised in the gas-phase by resonance-enhanced multi-photon ionisation within a set of velocity map imaging optics. The NO molecules preferentially leave the surface along the surface normal with a very narrow angular distribution, indicating a non-thermal desorption process.