Synchrotron radiation photoionization mass spectrometry of laser ablated species

The present paper describes an experimental apparatus suitable to create and study free clusters by combining laser ablation and synchrotron radiation. First tests on sulfur samples, S, showed the production, through laser ablation, of neutral Sn clusters (n = 1–8). These clusters were ionized using synchrotron radiation at photon energies from 160 eV to 175 eV, across the S 2p core edge. The feasibility of such combined ablation–synchrotron radiation experiments is demonstrated, opening new possibilities on the investigation of free clusters and radical

Dynamic Response of CVD Monocrystalline Diamond to Low-Energy X-ray Beam

"Detectors sensitive to ionizing radiations were assembled from high-purity single-crystal diamond plates with Ti\/Au injecting contacts. Spectrally resolved photoconductivity measurements in the range 2-6 eV were used to infer the defect density in the diamond bulk material using silver contacts. The electrical behavior of annealed Ti\/Au contacts was analyzed in the dark through current-voltage measurements in the range ±500V (104 V\/cm). Although contacts appear to be ohmic in the dark, two different transport regimes were found under x-ray irradiation as a function of the applied bias voltage. Recombinative regime at low bias and space charge limited injection regime at high bias were evidenced. The analysis of the photocurrent’s module and phase under x-ray modulated irradiation allowed us to highlight photoconductive gain phenomena mitigated by a Poole-Frenkel field-assisted detrapping process. Through the analysis of device’s impedance under irradiation, a lumped-elements electrical circuit is proposed to explain the detector’s dynamic behavior.

Characterization of the activity of (+)-usnic acid and its new derivatives against M. tuberculosis and selected non-tuberculous mycobacterium strains

Due to the rising incidence of tuberculosis (TB) worldwide and the emergence of multidrug resistant (MDR) strains, the development of new antituberculous drugs to reduce the duration of the treatment and fight MDR-TB is urgently needed. Usnic acid is reported to have antimycobacterial properties in vitro on susceptible and resistant strains, but because of its rapid metabolism and toxicity prevents further exploitation. The aim of this study is to characterize the activity of usnic acid and its derivatives, against M. tuberculosis susceptible, resistant and MDR strains and selected non-tuberculous mycobacterium strains

Oxidation of the 8 × 8-reconstructed ˇ-Si3N4(0 0 0 1) surface:A photoemission study

The thermal oxidation of the beta-Si3N4(0 0 0 1)-8 × 8 surface has been carried out. The spectroscopic characterization has been performed by high resolution core-level and by angle-resolved photoemission spectroscopy. Our findings demonstrate that the surface shows a low but clear reactivity with oxygen. The known resonance ascribed to the 8 × 8 reconstruction results strongly affected by the oxygen dosing, demonstrating the involvement of the topmost nitride atoms

Synchrotron radiation photoionization mass spectrometry of laser ablated species

5 pags, 4 figsThe present paper describes an experimental apparatus suitable to create and study free clusters by combining laser ablation and synchrotron radiation. First tests on sulfur samples, S, showed the production, through laser ablation, of neutral Sn clusters (n = 1-8). These clusters were ionized using synchrotron radiation at photon energies from 160 eV to 175 eV, across the S 2p core edge. The feasibility of such combined ablation-synchrotron radiation experiments is demonstrated, opening new possibilities on the investigation of free clusters and radicals. © 2009 Elsevier B.V. All rights reserved.J. Alvarez thanks CNR and the Short-Term-Mobility Program for travel and accommodation expenses. J. Alvarez and M. Sanz wantalso to thank CSIC-CAM support under the Project CCG07-CSIC/ESP-2213 for travel and equipment. A.Casu acknowledges ‘‘Sardegna Ricerche” for funding his visit at INFM-TASC. A.M. Juarez-Reyesand L.M. Hoyos kindly acknowledge the support of ICTP. J. Alvarezand M. Stankiewicz thank EU support from VII Framework Program Transnational Access during the experiments at the Elettra Synchrotron Facilit