13 research outputs found
Classical-quantum correspondence in atomic ionization by midinfrared pulses: Multiple peak and interference structures
Atomic ionization by strong and ultrashort laser pulses with frequencies in the midinfrared spectral region have revealed novel features such as the low-energy structures. We have performed fully three-dimensional quantum dynamical as well as classical trajectory Monte Carlo simulations for pulses with wavelengths from λ=2000 to 6000 nm. Furthermore, we apply distorted-wave quantum approximations. This allows to explore the quantum-classical correspondence as well as the (non) perturbative character of the ionization dynamics driven by long-wavelength pulses. We observe surprisingly rich structures in the differential energy and angular momentum distribution which sensitively depend on λ, the pulse duration τp, and the carrier-envelope phase ϕCEP
Low-energy peak structure in strong-field ionization by mid-infrared laser-pulses: two-dimensional focusing by the atomic potential
We analyze the formation of the low-energy structure (LES) in above-threshold
ionization spectra first observed by Quan et al.\ \cite{quan09} and Blaga et
al.\ \cite{blaga09} using both quasi-classical and quantum approaches. We show
this structure to be largely classical in origin resulting from a
two-dimensional focusing in the energy-angular momentum plane of the
strong-field dynamics in the presence of the atomic potential. The peak at low
energy is strongly correlated with high angular momenta of the photoelectrons.
Quantum simulations confirm this scenario. Resulting parameter dependences
agree with experimental findings \cite{quan09,blaga09} and, in part, with other
simulations \cite{liu10,yan10,kast11}.Comment: 12 pages, 6 figure
X-ray powder crystallography with vertex instrumentation
Summarization: An X-ray Diffractometer for Powder Crystallography is described along with experimental results and future plans. This is an intermediate instrument toward a long linear array system. Three channels of a silicon microstrip detector, are the detecting elements in the present instrument. Each detector channel is followed by a VLSI readout chain, which consists of a charge preamplifier with pulse shaping circuitry, a discriminator, and a 16-bit counter. Control and data acquisition is performed with a custom made PC readout card. A motorized goniometer scans the angle range of interest. Calibration of the system is done with reference samples and data which are captured with a one-channel conventional NaI detector.Presented on: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipmen