Real-Time Monitoring of the Pulsed Laser Ablation of Metals Using Ablation Plasma Spectroscopy

Here we demonstrate that the emission spectra of the ablation-plasma produced by nanosecond laser pulses on metallic Al targets may be directly connected to the ablation rates and the dimensions of the ablated craters. We show that the variation of the individual spectral-lines intensities with pulse number gives direct, real-time information on the crater depth, whereas the relative intensities of the lines and their widths enable us to study the variation of the electron temperature and density with pulse number and laser fluence in direct connection to the ablation rates. To interpret these results we use a simple model in which the plasma-plume is treated as an ideal gas expanding away from the target with a velocity given by the electron-temperature, and exerting a recoil pressure determined by the electron temperature and density. The model correlates the plume hydrodynamic-length to the crater dimensions and succeeds in predicting the rims heights.     

Paolo Pizzetti: The forgotten originator of triangle comparison geometry

The theorem comparing the angles of two geodesic triangles with the same side lengths lying on surfaces with different curvatures, commonly attributed for the two-dimensional case to A.D. Alexandrov (1948) and for the n-dimensional Riemannian case to V.A. Toponogov (1959), goes back, for the two-dimensional case, to Paolo Pizzetti (1907b). Besides suggesting a correction of the historical narrative regarding the development of comparison geometry, the present note also mentions possible reasons for the oversight.     

An arrayed nanoantenna for broadband light emission and detection

We suggest a broadband optical unidirectional arrayed nanoantenna consisting of equally spaced nanorods of gradually varying length. Each nanorod can be driven by near‐field quantum emitters radiating at different frequencies or, according to the reciprocity principle, by an incident light at the same frequency. Broadband unidirectional emission and reception characteristics of the nanoantenna open up novel opportunities for subwavelength light manipulation and quantum communication, as well as for enhancing the performance of photoactive devices such as photovoltaic detectors, light‐emitting diodes, and solar cells. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and thermal behavior of some diisocyanate–silane compounds

Some silica-organic compounds were prepared by an addition reaction between γ-amino-propyl-triethoxy silane and 4,4′-diphenylmethane diisocyanate. The obtained products were characterized by FTIR spectrometry. The essential synthesis parameter was the molar ratio between the two reactants. The thermal behavior of the products was rather good, until 150 °C no mass loss or thermal effects being observed. The thermal behavior was determined under non-isothermal conditions, using TG/DTG/HF diagrams. Due to the hydroxyl end-groups, these compounds are recommended for adhesives between organic and inorganic surfaces.