The interaction of light and matter is of fundamental interest to the fields of both physics and chemistry. Advances in laser technology continually push the interaction to higher energies, reaching unexplored intensities in which new science is emerging. Very intense laser pulses remove electrons from atoms through the quantum mechanical process of tunneling. This "strong-field ionization" is the birthing process for electrons involved in many important physical phenomena including high-harmonic generation, orbital tomography, attosecond pulse generation, and novel forms of lithography. My research is aimed at investigating the fine details of this process, including the enhanced ionization phenomena that occurs in large molecules and clusters. Gaining a better understanding of electron interaction effects and their involvement in strong-field ionization has important consequences for further developing techniques of using intense laser pulses to measure the electronic properties of molecules, clusters, and solid state materials.
I am interested in learning how quickly electrons can respond to ultrashort (femtosecond or even attosecond) laser pulses. Using gas-phase optics, we generate a table-top x-ray laser that has the ultimate temporal resolution characterized in the attosecond timescale. An attosecond is defined as a billionth of a billionth of a second, and is the timescale of electron motion. This isolated attosecond laser pulse is sensitive to not only the element, but also the oxidation state, electronic spin state, and charge state of the atoms, while also having the time resolution to monitor the changes in real time. This unparalleled view of electron motion allows us to finally resolve electron dynamics and gain a fine understanding of how electrons transfer between atoms and across molecules. By monitoring the first instances electron motion, we explore how various pathways influence the outcome of a chemical reaction or photoexcitation.
Isolated aggregates of atoms or molecules compose a new phase of matter, known as clusters, and have unique physical properties. In the clustered domain, the addition or subtraction of a single atom can dramatically effect the properties of the material. We study the conditions, structure, and electronic properties that make a certain cluster stable and useful. Individual clusters can be combined together as building blocks in a bottom-up approach for the design of new materials with tailored properties.