Friday, December 9, 2005

Prof. Jan Chaloupka

Dept of Physics, College of William & Mary

"Atoms in Intense Laser Fields: the photoelectric effect under extreme conditions"

2:00 pm in room P-148

Abstract: In 1905, Einstein used the idea of light quantization to explain the photoelectric effect. Since light came in discrete bundles of energy whose magnitude was determined by color, weak red photons could not liberate electrons from a surface regardless of the brightness of the light. Strong blue photons, however, could easily do the job. Some sixty years later, the idea of probing matter with light entered into a new regime with the invention of the laser. Extremely high intensities could be created by tightly focusing an ultrashort pulse of laser light. Now, instead of being restricted to only one chunk of light at a time, an atom could absorb multiple photons simultaneously. As a result, weak photons could conspire together to strip electrons from an atom. This process, known as multiphoton ionization, has been studied extensively for over two decades. We present the results from our studies of double ionization, showing how two electrons can work together to escape from the atom, improving their chance for freedom a thousand-fold over working alone.