Photon stimulated desorption of and nuclear resonant scattering by noble gas atoms at solid surfaces

TL;DR

This paper investigates photon stimulated desorption of xenon atoms from gold surfaces and nuclear resonant scattering of krypton on titanium oxide, revealing non-thermal and thermal desorption pathways and the potential of noble gases as surface probes.

Contribution

It presents experimental insights into desorption mechanisms and nuclear resonant scattering involving noble gas atoms at solid surfaces, highlighting new pathways and probing techniques.

Findings

Identification of non-thermal and thermal desorption pathways.

Thermal desorption flux dependence and velocity predictions.

Noble gases as probes of electric field gradients at surfaces.

Abstract

When a noble gas atom approaches a solid surface, it is adsorbed via the Van der Waals force, which is called physisorption. In this thesis, several experimental results concerning physisorbed atoms at surfaces are presented. First, photon stimulated desorption of Xe atoms from a Au substrate using nano-second laser is presented. With the time-of-flight measurements, the translational temperature and the desorption yield of desorbing Xe as a function of laser fluence are obtained. It is discovered that there are non-thermal and thermal desorption pathways. It is discussed that the former path involves a transient formation of the negative ion of Xe. The desorption flux dependence of the thermal pathway is also investigated. We found that at a large desorption fluxes the desorption flow is thermalized due to the post-desorption collisions. The resultant velocity and the temperature of the flow is found to be in good agreement with the theoretical predictions based on the Knudsen layer formation. Lastly, nuclear resonant scattering of synchrotron radiation by the multi- and mono-layer of $^{83}$Kr at a surface of the titanium oxide is presented. The use of the noble gas atoms as the probes of the electric field gradient at the solid surfaces is discussed.