Ultrashort pulses of intense, coherent, and tunable far-infrared (FIR) and mid-infrared (MIR) radiation, achievable with freeelectron lasers (FELs) and optical parametric amplifiers (OPAs), provide unique opportunities to investigate low energy dynamics in solids. This paper reviews our recent experiments on bulk and quantum-confined semiconductors using such radiation. These experiments includ...

We consider a PDE system comprising compressible hydrodynamics, flux-limited diffusion radiation transport and chemical ionization kinetics in a cosmologicallyexpanding universe. Under an operator-split framework, the cosmological hydrodynamics equations are solved through the Piecewise Parabolic Method, as implemented in the Enzo community hydrodynamics code. The remainder of the model, compri...

Ultrafast betatron x-ray emission from electron oscillations in laser wakefield acceleration (LWFA) has been widely investigated as a promising source. Betatron x-rays are usually produced via self-injected electron beams, which are not controllable and are not optimized for x-ray yields. Here, we present a new method for bright hard x-ray emission via ionization injection from the K-shell elec...

A radiative transfer scheme is presented, based on a moment description of the equation of radiative transfer and the so–called “M1 closure model” for the Eddington tensor. This model features a strictly hyperbolic transport step for radiation : it has been implemented using standard Godunov–like techniques in a new code called ATON. Coupled to simple models of ionization chemistry and photo-he...

We present the observation of an autoionization cesium 37D5/2 Rydberg atoms in ultracold gases and analyze mechanism. The process is investigated by varying delay time tD atomic density. dependence ionization signals on density shows that has effect not only initial ion but also evolution atoms. results reveal mostly attributed to blackbody radiation (BBR)-induced photoionization, BBR-induced t...

Air kerma calibration coefficients for a reference class ionization chamber from narrow x-ray spectra and cesium 137 gamma-ray beams were compared between the National Institute of Standards and Technology (NIST) and the Kenya Bureau of Standards (KEBS). A NIST reference-class transfer ionization chamber was calibrated by each laboratory in terms of the quantity air kerma in four x-ray referenc...

2014 A one-dimensional model oriented toward a thorough understanding of line and continuum emission from a CO2 laser-induced helium plasma is presented. The model combines a time-dependent calculation of the ionization and radiation dynamics with a lagrangian hydrodynamic simulation code. Detailed collisional radiative models involving many neutral and ion excited levels are used to predict th...

The line ratios from coronal gas in Seyferts can be successfully fitted with photoionized clouds of high densities and low volume filling factor. The ionization parameter implied is sufficiently high that models must consider the effect of radiation pressure from the active nucleus. In spite of the nucleus gravitational force, radiation pressure is sufficiently strong to compress and radially a...

Ionizing radiation is electromagnetic radiation that has sufficient energy to remove electrons from atoms. Ionization results in the production of negatively charged free electrons and positively charged ionized atoms. Ionizing radiation can be classified into two categories: photons (X-radiation and gamma radiation) and particles (alpha and beta particles and neutrons). Five types or sources o...