RESUMO
We present a theoretical and experimental study of the production of very high order photoelectrons from alkali metal atoms interacting with intense, midinfrared radiation. The strength of this process shows an unexpectedly strong species dependence. We find that this dependence can be explained via the difference in the cross section for electron-ion scattering from the different atoms. This allows us to directly relate the high energy portion of the photoelectron spectrum to specific features of the electron-ion potential.
RESUMO
A high-gain harmonic-generation free-electron laser is demonstrated. Our approach uses a laser-seeded free-electron laser to produce amplified, longitudinally coherent, Fourier transform-limited output at a harmonic of the seed laser. A seed carbon dioxide laser at a wavelength of 10.6 micrometers produced saturated, amplified free-electron laser output at the second-harmonic wavelength, 5.3 micrometers. The experiment verifies the theoretical foundation for the technique and prepares the way for the application of this technique in the vacuum ultraviolet region of the spectrum, with the ultimate goal of extending the approach to provide an intense, highly coherent source of hard x-rays.
