An experiment for two-colors photoionization using high intensity extreme-Uv free electron and near-IR laser pulses

International audienc

Characterization of the FLASH XUV-FEL pulses by two-color photoionization experiments

The current key performance indicators of the pump-probe facility at the Free Electron Laser in Hamburg (FLASH) are described. The temporal and spatial characteristics of both the extreme ultra-violet (XUV) Free Electron Laser and the temporally synchronized optical femtosecond Ti:Sapphire laser are determined by measuring two-color above threshold ionization in rare gases. Characteristic sidebands appear in the photoelectron spectrum under the combined action of both radiation fields providing a very sensitive probe for the spatial and temporal overlap of both pulses. The high spatial acceptance of a magnetic bottle electron spectrometer enabled us to obtain single-shot photoelectron spectra and to correct for the inherent time jitter between both light sources, which reduces the temporal resolution when recording spectra in average mode. As an illustration of the first application, % of the pump-probe set-up, experimental results on polarization control in the two-photon two-color ionization of atomic He are presented

An experiment for two-color photoionization using high intensity extreme-UNT free electron and near-IR laser pulses

We describe an experimental system designed for single-shot photoelectron spectroscopy on free atoms and molecules at the Free Electron Laser in Hamburg (FLASH at DESY). The combination of the extreme ultra-violet (EUV) Free Electron Laser and a temporally synchronized optical fs laser (Ti:Sapphire) enables a variety of two-color pump-probe experiments. The spectral, temporal and spatial characteristics of both the EUV FEL and the optical laser pulses, the experimental procedure to control their overlap as well as the performance of an electron spectrometer used to obtain single-shot photoelectron spectra are discussed. As an illustration of the capabilities of this set-up, some results on two-photon two-color ionization of rare gases are presented

Long-range order and short-range order study on CoCrPt/Ti films by synchrotron x-ray scattering and extended x-ray absorption fine structure spectroscopy

10.1063/1.1448799Journal of Applied Physics9110 I7182-7184JAPI

Polarization Control in Two-Color Above-Threshold Ionization of Atomic Helium

Two-color multiphoton ionization of atomic helium was investigated by combining extreme ultraviolet (XUV) radiation from the Free Electron Laser in Hamburg with an intense synchronized optical laser. In the photoelectron spectrum, lines associated with direct ionization and above-threshold ionization show strong variations of their amplitudes as a function of both the intensity of the optical dressing field and the relative orientation of the linear polarization vectors of the two fields. The polarization dependence provides direct insight into the symmetry of the outgoing electrons in above-threshold ionization. In the high field regime, the monochromaticity of the XUV radiation enables the unperturbed observation of nonlinear processes in the optical field