Electron temperature in the plasma of a spark-recombination laser, The

Includes bibliographical references (page 4451).The electron temperature in an expanding spark plasma used as active medium in a cadmium recombination laser was measured using the relative intensities of helium lines originated from levels in local thermodynamic equilibrium. Measurements resolved in space and time show that the electron temperature at the conditions of maximum gain are 1000 and 600 K at 5 and 10 mm of the sparks, respectively. Rapid cooling occurs after the termination of the discharge-current pulse, and the electron temperature reaches values below 1000 K. Subsequently, the electron temperature decrease is slow. The optical gain calculated for the 1.43-μm Cd (I)-recombination-laser transition using the measured electron temperature and particle density values is 3 × 10-3 cm-1, in good agreement with measurements

Sizing gold nanoparticles by optical extinction spectroscopy

The measurement of optical extinction is used to determine the size of nearly spherical gold nanoparticles suspended in solution, produced by a 'reverse micelles' process. The contrast between the maximum and the minimum in the extinction spectra around 450 and 520 nm shows a linear dependence with the mean radius of the gold particles less than 3 nm; however, the method can be used to size particles up to 7 nm. Experimental results for extinction spectra can be fitted by Mie's theory if the optical constants from bulk material values are modified by introducing the limitation of the mean free path due to collisions of conduction electrons with the boundary of the nanoparticles.Facultad de Ciencias ExactasCentro de Investigaciones Óptica

Sizing gold nanoparticles by optical extinction spectroscopy

The measurement of optical extinction is used to determine the size of nearly spherical gold nanoparticles suspended in solution, produced by a 'reverse micelles' process. The contrast between the maximum and the minimum in the extinction spectra around 450 and 520 nm shows a linear dependence with the mean radius of the gold particles less than 3 nm; however, the method can be used to size particles up to 7 nm. Experimental results for extinction spectra can be fitted by Mie's theory if the optical constants from bulk material values are modified by introducing the limitation of the mean free path due to collisions of conduction electrons with the boundary of the nanoparticles.Facultad de Ciencias ExactasCentro de Investigaciones Óptica

Photoacoustic characterization of phase transitions in amorphous metal alloys

In this work a pulsed laser photoacoustic technique is employed in amorphous alloys for the characterization of crystallization temperatures and the determination of the activation energies for the transitions. It is shown that the changes produced in the photoacoustic signal generated by low energy laser pulses (< 200 μJ), is a sensitive probe for detecting the crystallization of a metallic amorphous sample. A piezoelectric transducer attached to the sample by means of a glass substrate was used for the acoustic detection. The developed technique has the advantages of requiring a minimum amount of sample, with no special sample preparation or conditioning. In order to demonstrate the validity of the technique, it was applied to the study of the crystallization processes of the amorphous Mg-Zn alloy, comparing the result with respect to resistivity measurements

Sizing gold nanoparticles by optical extinction spectroscopy

The measurement of optical extinction is used to determine the size of nearly spherical gold nanoparticles suspended in solution, produced by a 'reverse micelles' process. The contrast between the maximum and the minimum in the extinction spectra around 450 and 520 nm shows a linear dependence with the mean radius of the gold particles less than 3 nm; however, the method can be used to size particles up to 7 nm. Experimental results for extinction spectra can be fitted by Mie's theory if the optical constants from bulk material values are modified by introducing the limitation of the mean free path due to collisions of conduction electrons with the boundary of the nanoparticles.Facultad de Ciencias ExactasCentro de Investigaciones Óptica

A xenon ion pumped open dye stream laser

A pulsed xenon ion laser with an output power of 1 kW over the blue-green lines was used to pump an open dye stream laser. An efficiency of the order of 40 percent was determined in broad-band mode operation. The bandwidth in this case was 48 nm (from 582 to 630 nm).Centro de Investigaciones Óptica

Sizing gold nanoparticles by optical extinction spectroscopy

The measurement of optical extinction is used to determine the size of nearly spherical gold nanoparticles suspended in solution, produced by a &#39;reverse micelles&#39; process. The contrast between the maximum and the minimum in the extinction spectra around 450 and 520 nm shows a linear dependence with the mean radius of the gold particles less than 3 nm; however, the method can be used to size particles up to 7 nm. Experimental results for extinction spectra can be fitted by Mie&#39;s theory if the optical constants from bulk material values are modified by introducing the limitation of the mean free path due to collisions of conduction electrons with the boundary of the nanoparticles