Strong-field Ionization Leading To Coulomb Explosion of Small Clusters
Open Access
- Author:
- Ross, Matthew W
- Graduate Program:
- Chemistry
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- September 14, 2012
- Committee Members:
- Albert Welford Castleman Jr., Dissertation Advisor/Co-Advisor
James Bernhard Anderson, Committee Member
William George Noid, Committee Member
Robert John Santoro, Committee Member - Keywords:
- strong-field
clusters
coulomb explosion
ionization enhancement
ultrafast laser
superatom - Abstract:
- The strong-field interaction of electromagnetic radiation with matter is an important area of study for understanding the specific mechanisms of ionization. Clusters are unique in that the addition or subtraction of a single atom can change the overall electronic properties of the system. Highly energetic processes is an emerging branch of physics focusing on the interaction of matter and strong radiation/particles. The Coulomb explosion of clusters is known to be an efficient source for producing multiply-charged ions through an enhancement in ionization. Intensity-resolved visible laser excitation experiments are compared with semi-classical theory to give insight into the mechanism through which ionization occurs in different atomic and cluster species. Under laser intensities that are predicted by theory to only singly ionize individual molecules, we have observed ions depleted of all valence electrons. An enhancement in ionization of nearly three orders of magnitude was observed in metal oxide clusters. This ionization behavior is attributed to occur in part through collective electron effects arising from nonadiabatic electron dynamics where upon tunneling plays an important role. Metal-containing clusters show ionization behavior that is highly dependent on the properties of the metal. Electrons in d and f-orbitals are delocalized, allowing for greater collective electron effects (such as ionization ignition, non-adiabatic electron dynamics, and electron impacts) to occur and thus, larger enhancements in ionization are observed in metal-containing clusters. Additionally, the degree of ionization enhancement is dependent on the type of bonding exhibited within the cluster. Stronger intermolecular interactions lead to greater enhancements in ionization.