1,721,004 research outputs found
Absorption and saturation mechanisms in aluminium laser ablated plasmas
No full textWe have measured time-of-flight (TOF) distributions of positive ions in plasmas produced by laser ablation of Al targets at the second (lambda = 532 nm) and third (lambda = 355 nm) harmonic of Nd:YAG laser radiation. The investigation has been carried out in a regime of relatively high laser fluences (1-60 Jcm(-2)). The interpretation of the ion TOF distributions in terms of theoretical shifted Maxwell-Boltzmann distributions produces a good agreement with the experimental data. This has allowed us to infer the ion flow velocity and temperature associated with the measured TOF distributions, as well as the ion kinetic energies as a function of the laser fluence. We have also studied the total ion yield at different laser fluences. Our results show that all the plume parameters investigated are increasing functions of the laser fluence until a saturation plateau is reached at high fluences (> 20 Jcm(-2)). We ascribe this saturation behaviour to strong absorption and partial, or total, reflection of the laser light by the hot plasma produced by the leading edge of the intense laser pulse. This interpretation is supported by a semi-quantitative analysis of the laser photon absorption and ionization mechanisms in Al plasma, at both laser wavelengths
MODULATION OF THE CONFORMATIONAL BEHEVIOR OF A-beta-(25-35) BY INTERACTION WITH NATURAL COMPOUNDS.
No full textThermal and nonthermal ion emission during high-fluence femtosecond laser ablation of metallic targets
No full textWe have investigated the emission of positive ions from metallic targets irradiated with intense, ultrashort laser pulses (approximate to 120 fs) at 780 nm, in both S and P polarized states. The measured energy spectra show the presence of a nonthermal, high-energy (several keV) ion component accompanying low-energy ions (tens of eV) produced by a thermal mechanism. The yield of the high-energy component shows a strong dependence on both laser fluence and light polarization. For the low-energy component a higher ablation efficiency was observed for P polarization, and ascribed to a more effective absorption mechanism active during the laser-target interaction. (C) 2000 American Institute of Physics. [S0003-6951(00)02549-3]
- …
