Rapid discharge-pumped wide aperture X-ray preionized KrF laser

A wide aperture X-ray preionized discharge-pumped KrF excimer laser has been constructed. A flat plate pulse-forming line (36 nF, 340 kV) charges a peaking capacitor (6 nF) through a rail-gap to facilitate a rapid discharge in the laser head. Collimated X-ray preionization is employed to obtain a wide and uniform discharge. The laser is intended to be used as a short pulse amplifier and results are presented when characterized as an oscillator. The active cross-section of the laser beam is 10×8 cm² with 50 cm effective electrode length. The laser pulse energy exceeds 4.7 J in a 28 ns pulse (FWHM).     

The Simulated Detection of the Objects at Variant Depth Using Depth-Adaptive Voxel Size Scheme in Diffuse Reflective Optical Tomography (DROT)

We study diffuse reflective optical tomography (DROT), aiming at the real-time imaging of the redox state change of the human cerebral cortex with the brain activity. In the uniform voxel size and simple regularization scheme we studied so far, the spatial resolution in the shallow region is unnecessarily good, whereas the noise and the sensitivity in the shallow region are too large to recover the signal in the depth. In this paper, we propose depth-adaptive voxel size reconstruction. By assigning wider lateral voxel size in the deep range, the relative sensitivity in the deep range is increased so that the signal in the deep range would be less masked by the presence of the unwanted target in the shallow range. We demonstrate that we can detect the deep objects without being masked by the shallow object using the proposed method.     

Subpicosecond UV pulse generation for a multiterawatt KrF laser

A 180-fs UV pulse has been generated based on a hybrid synchronously pumped mode-locked dye laser for a multiterawatt KrF laser system. The pulse width was measured by the single shot autocorrelation technique with the three-photon fluorescence of the XeF C-A transition. The pulse width broadening due to dispersive media was investigated. The results show that the observed pulse width broadening from 210 fs to 390 fs through the entire system is explained mostly by the linear dispersion of the optical elements for near-transform-limited input pulses.     

Type II photoreactions of α-alkyl β-oxoesters. Neighboring group effect on 1,4-biradical reactions and effective internal filter effect by the type II photoproduct

The α-alkyl β-oxoesters $\text{1}$ undergo type II photoreactions. The process of back hydrogen transfer in the 1,4-biradical intermediate to revert to the starting ester is suppressed because of the intramolecular hydrogen bonding between the hydroxyl and carboalkoxyl groups in the biradical intermediate. The hydrogen bonding determines the stereochemistry of 1,4-biradical cyclization. The cyclobutanols having the hydroxyl group cis to the carboalkoxyl group are formed exclusively from the α-alkyl β-oxoesters $\text{1}$. The enol form of the type II elimination product, the benzoylacetate $\text{2}$, acts as an effective internal filter for the photoreaction of the α-alkyl β-oxoester $\text{1}$.     

Temperature dependence of the electronic structure of Sr14Cu24O41 studied by resonant inelastic X-ray scattering

We report a resonant inelastic X-ray scattering (RIXS) study of charge excitations in the two-leg ladder Sr₁₄Cu₂₄O₄₁. RIXS spectra at 1–5 eV are found to be dependent on temperature. An intraband excitation of the ladder, which appears as a continuum intensity below the Mott gap, decreases in intensity with temperature. Because the intraband excitation is related to the dynamics of doped holes in the ladder, its decrease of the intraband excitation is attributed to the reduction of the mobile holes in the ladder at low temperature.