Exciton-driven highly hyperthermal O-atom desorption from nanostructured CaO

Photon and electron irradiation of insulating materials induces a wide range of phenomena, such as electron emission and sample charging, luminescence, structural changes, and desorption of ions and neutral atoms. The charge state and kinetic energy of the desorbed species depend upon excitation conditions, such as laser intensity, electron flux, and photon energy.

We report qualitatively new highly hyperthermal oxygen atom emission from nanostructured CaO excited by 6.4 eV nanosecond laser pulses. The kinetic energy distribution of emitted O-atoms peaks at 0.7 eV, which is over 4 times greater than previously observed for hyperthermal oxygen atom emission and approximately 20 times greater than the peak of the thermal kinetic energy distribution.

These experimental and theoretical results suggest that specific atomic desorption mechanisms in wide-bandgap materials can be controlled by selective electronic excitation of not only the surface but also the bulk of these materials.

For more information see:

• Excitation, Ionization, and Desorption: How Sub-Band Gap Photons Modify the Structure of Oxide Nanoparticles, Journal of Physical Chemistry C 113, 1274-1279 (2009).
• Laser control of desorption through selective surface excitations (feature article), Journal of Physical Chemistry B 109, 19563-19578 (2005).