Orientation dependence of high-order harmonic generation in molecules

Published versio

Finite element analysis of a shear punch test

The authors present new experimental data for shear punch tests and tensile tests using four different materials. The correlation between shear punch and tensile yield stresses must be established empirically, and the procedure for doing this is discussed. The elastic-plastic deformation in a shear punch test develops gradually with increasing punch displacement and is often assumed to be simple shear. This is examined using finite element analysis to simulate the development of plasticity during the early stages of punch displacement. The simulation results are used to rationalize the empirically established yield stress correlations

Ultrafast laser time-of-flight mass analysis of laser-desorbed atoms and molecules

Femtosecond time-of-fight mass spectra of laser-desorbed gallium arsenide (GaAs) and trinitrobenzene (TNB) reveal the characteristic features and differences of femtosecond atomic and molecular ionisation. Significant yields of multiply-charged atomic fragments, parent molecular ions and structure-specific fragment ions of labile molecules have been obtained. An optimum desorption laser intensity for the transfer of neutral intact parent molecules in to the gas phase has been observed to be molecule-dependent. This work demonstrates the potential of ultrafast laser ionisation and has significant implications for analytical and environmental studies of solid materials

Microstructure, texture and superplasticity of a fine-grained Mg-Gd-Zr alloy processed by equal-channel angular pressing

There are limited reports to date on the microstructure and superplasticity of the Mg-Gd alloys after processing by equal-channel angular pressing (ECAP). Accordingly, the effects of ECAP temperature from 473 K to 723 K (200 °C to 450 °C) and number of passes (2, 4, and 8) on the microstructure and texture of an extruded Mg-5Gd-0.4Zr (GW50) alloy were investigated by scanning electron microscope, transmission electron microscope, and electron backscattered diffraction. The results show that the optimum ECAP temperature is 623 K (350 °C). Higher temperatures give extensive grain growth and the material has insufficient formability at lower temperatures. The results show also that the alloy exhibits no further grain refinement after four ECAP passes and there is slight grain growth at 8 ECAP passes. Samples were processed by four passes at 623 K (350 °C) and then subjected to shear punch testing. The results confirm the occurrence of superplastic behavior at 723 K (450 °C) with a maximum strain rate sensitivity index of ~0.47 and an activation energy of ~110 kJ mol-1. The results are consistent with the occurrence of flow by grain boundary sliding in the superplastic region