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Intense-field ionization of atoms and molecules: Spatially resolved ion detection and ultrashort optical vortices

James Strohaber, University of Nebraska - Lincoln


The interaction of light and matter has for many years provided a venue in which scientists have been able to increase their understanding of fundamental quantum mechanics and electromagnetism. The advent of the laser in the early sixties significantly changed the way in which experiments were performed. These coherent sources of radiation played a pivotal role in the investigations of new phenomenon such as multiphoton ionization. As time progressed many significant advances have been made in laser technology. For instance, the development of mode-locking techniques such as Q-switching and the nonlinear Kerr effect have made pulsed lasers possible (now down to ∼ 5 fs), the discovery of Chirped-Pulse-Amplification allowed for these ultrashort pulses to be amplified up to Joules in energy per pulse. As a result of these new advances in laser technology, new and exciting physics have been illuminated. When ultrashort intense laser fields interact with matter, one possible outcome is the ionization of the target into its constituents (atoms, molecules, electrons or photons). Because the constituents are usually ions which may have different masses and charges, time-of-flight (TOF) techniques are often employed in the analysis of the ionization yields. In these experiments, the usual quantity of physical interest is the ionization probability as a function of a well known intensity. However, in reality the impinging laser radiation possesses a distribution of intensities. To further add to this annoyance, it is difficult for a TOF spectrometer to distinguish between ions created at different intensities and the usual course of action is to integrate ions from over the entire focal volume. The inevitable result of this so-called spatial averaging is to limit information about the underlying physical process. Additionally, coherent sources of radiation have captured the attention of researchers whose main interests are in spatially modulating the phase and amplitude of laser beams. Encoding beams of light with information has had significant impact over a broad range of disciplines from the detection of extrasolar planets to the manipulation of DNA. On the forefront of this research is an exotic mode of light known as an optical vortex. The uniqueness of the optical vortex is that it carries a sharp amount of optical orbital angular momentum. The manipulation of laser beams also provided a tool for the coherent control of electrons which may be useful in the production of high harmonic generation and attosecond pulse generation. With new advances in technology we are now able to perform experiments which were previously impossible to carryout. And with these new experiments, novel and powerful techniques must be incorporated to render meaningful data governing the underlying quantum processes.

Subject Area

Molecular physics|Atoms & subatomic particles|Optics

Recommended Citation

Strohaber, James, "Intense-field ionization of atoms and molecules: Spatially resolved ion detection and ultrashort optical vortices" (2008). ETD collection for University of Nebraska - Lincoln. AAI3297758.