Coherence in high temperature systems represents a challenge due to the plethora of dephasing processes. We recently reported the dynamic Rabi oscillation with manifestation of broad bandwidth emission in a laser-induced microplasma, where electron temperatures approach 10,000K. Using a strong field laser pulse of picosecond duration, we show that the broad band emission produced in the effect is coherent and can be described using a time-dependent generalized Rabi theory. We model the spatial-spectral emission profile and demonstrate control of the dynamic Rabi emission using shaped pump pulses. Simulation of the spectral phase reveals that the emission is compressible to 10 femtosecond features. Control of the dynamic Rabi oscillation in a pump probe scenario is then considered using a Bloch sphere model.
The second strong field phenomena to be presented involves vaporization of complex biological macromolecules using ultrafast and ultraintense laser pulses with intensity of ~10^13 W cm^-2. Again, we found an interesting new phenomena, vaporization of intact folded protein into the gas phase, under conditions where complete decomposition of the protein was anticipated. As in the dynamic Rabi effect, the ultrafast nature of the strong laser field energy deposition localizes excitation to a limited number of channels, here laser field couples exclusively to translational energy of protein. The state of vaporized protein is detected using electrospray ionization and a new method for condensed phase protein structure determination will be described.
Levis pioneered the area of strong field chemistry, which is the use of ultrafast and intense lasers to modify, manipulate and detect molecular systems. This work involves experimental and theoretical investigations of lasers having electric field strength of magnitude equal to the forces binding electrons to molecules. Recent work combines strong laser fields with condensed phase systems to induce intact vaporization of biological macromolecules and explosives, the development of filament-based impulsive Raman spectroscopy for gas phase detection and the discovery of the dynamic Rabi oscillation in strong fields. The Levis laboratory has demonstrated the use of intense lasers to produce new molecular signatures for mass spectrometry and the use of pulse shaping to modify these signatures.