V R González

Measurement of Stark broadening and shift of singly ionized Ar lines

A very extensive compilation of Stark widths and shifts for more than 125 Ar II visible spectral lines is presented in this work. These atomic parameters have been measured in a pulsed discharge lamp by using different mixtures of pure argon or argon and helium. The electron density, which typically ranges from 0.2 to has been determined interferometrically and, in the case of pure argon plasmas, also spectroscopically from -Stark broadening. The Ar II excitation temperature (15 000-31 000 K) has been determined by Boltzmann-plot techniques from the intensity of Ar II lines. A detailed description of all the relevant points in this kind of measurement is given. Comparisons with most of the data published about this topic for Ar II are also included.

Stark broadening and shift measurements of visible Si II lines

A set of experimental Stark width and shift parameters of visible singly ionized silicon spectral lines is reported in this paper. Measurements have been made on a pulsed plasma generated in a linear discharge lamp filled with a mixture of silane and helium. Electron density and temperature in this plasma range from 0.2 to 0.9 × 1023 m−3 and from 16 000 to 20 000 K respectively. Electron density has been simultaneously determined by two-wavelength interferometry and from Stark broadening of He I 501.6 nm, He I 728.1 nm and Hα lines. Temperature has been simultaneously determined from a Boltzmann plot of He I lines, from absolute emission of He I lines and from a Boltzmann plot of Si II lines. Dependences of measured Stark parameters on electron density and temperature have been investigated and the final results have been compared with most of the previous experimental data as well as with some theoretical models.

Experimental measurement of corneal haze after excimer laser keratectomy.

We developed a model of corneal haze following photorefractive keratectomy (PRK) in Iber Braun hens and studied optical properties. The animals underwent PRK for -9.0 diopters of myopia and were divided into groups based on treatment with different wound-healing modulators. At different time points postoperatively, we evaluated haze by slit-lamp microscopy. An experimental device was developed to measure transmittance spatial maps and forward scattering of He-Ne laser light in the excised corneas. Subjective and objective haze measures were compared for each group at the different times. Keratocyte densities were determined by optical microscopy and keratocyte sizes by electron microscopy. The agreement between experimental results and a simple numerical model of scattering suggests that increases in stromal keratocyte density after PRK might explain the degree of corneal haze.

Measurement of Stark broadening and shift of visible N II lines

This work reports information about Stark broadening and shift parameters of a very extensive collection of visible singly ionized nitrogen lines. All of them were measured in a linear discharge lamp from a mixture of nitrogen and helium. Electron density and temperature range in this experiment from 0.2 to 1.1 × 1023 m-3 and from 17 000 to 29 000 K, respectively. The first one has been simultaneously determined from two-wavelength interferometry and from the Stark broadening of He I 471.3 nm, the second from a Boltzmann plot of N II lines and from N II/N I intensity ratios. Dependences of these Stark parameters with temperature and electron density have been investigated and the final results have been compared with most of the previous experimental data as well as with two theoretical models. All relevant details relative to this experiment are given in the paper.

Quantitative and functional influence of surround luminance on the letter contrast sensitivity function.

Aim:  To determine the influence of surround luminance on the letter contrast sensitivity function.

Experimental measurements of shifts and asymmetries of He II Pα and Pβ spectral lines

Red shifts and asymmetries of He II Pα 468.5682 nm and Pβ 320.3104 nm lines were measured in a pulsed plasma at an electron density measured by two-wavelength interferometry which ranges from 5.54 × 1022 m−3 to 7.48 × 1022 m−3 with uncertainty of 10%. Temperature ranges from 1.70 to 1.83 eV, and has been determined from intensities ratio of Pα and Pβ lines. Shifts for these lines were obtained using as reference lines Cd I 467.8149 nm and He I 318.7745 nm respectively. Measurements of asymmetries have been represented using reduced wavelength units. All results have been compared with previous experimental and theoretical data.

Stark parameters of neutral helium 318.8 nm line

Aims. Our aims is to measure with good accuracy the Stark parameters (width and shift) of the He I 318.8 nm (2s 3 S-4p 3 P°) line and to calibrate Stark width and shift dependencies of this line as a function of the electron density. In this way, it is possible to obtain an alternative method of diagnosing the plasmas of astrophysical origin and to check the quality of theoretical models that predict these parameters. Methods. We made a spectroscopic and interferometric analysis of a pulsed plasma. The electron temperature was obtained with an intensity ratio of He II lines and ranges from 19000 to 23000 K. Electron density was determined by interferometry ranging from 1.25 × 10 22 m -3 to 6.22 × 10 22 m -3 . Results. These experimental results are new for these plasma conditions. When joined with previous bibliographic data, they allowed us to obtain an empirical calibration expression for the Stark width and the shift of this line in a broad range of electron densities. Comparisons with different theoretical models are also included.

Measurement of Stark broadening and shift constants of singly ionized krypton lines

Stark widths and shifts of 25 visible singly ionized krypton lines are presented in this paper. All of them were measured in a pulsed discharge lamp from a mixture of krypton and helium. The electron density, which typically ranges from 0.2 to 1.8×1023 m-3 has been simultaneously determined from two-wavelength interferometry and from the Stark broadening of the He I 388.865 nm. The excitation temperature, from 16 000 to 24 500 K, has been measured from the Boltzmann plot of Kr II lines, which has allowed us to recalculate some Kr II transition probabilities. Comparisons with most of the data published to date about this topic in Kr II are also included.

Measurement of Excitation equilibrium departure evolution in an argon pulsed plasma

This work reports information about the temporal evolution of the excitation equilibrium departure in a high current pulsed arc. An argon plasma has been created in a linear lamp by discharging a capacitor bank on its electrodes. Spatially and temporally-resolved measurements have allowed us to determine electron density N e and excitation temperature T with great accuracy. Single-wavelength interferometry and H α -Stark broadening have been used to measure N e (0.2–0.98× 10 23 m -3 ). Excitation temperature has been obtained from Boltzmann-plot of ArII lines and ranges in this experiment from 13500 to 26500 K. By assuming this temperature is equal to kinetic electron temperature and by comparing the theoretically predicted and the experimental ArII/ArI intensities ratios at each instant of the plasma life, it is possible to measure the departure of the excitation processe from local them dynamic equilibrium (LTE) conditions and to show the ionizing characteristics of this close-to-LTE plasma. Different t...

Precise measurement of the Balmer-alpha core

Abstract We have obtained a precise spectrum of the Balmer-alpha line, corrected for self-absorption effects, from a constant-electron-density plasma with different optical depths, in order to compare it with theoretical models and simulation techniques. The reconstruction process of the non-self-absorbed profile is highly reproducible and may be applied to both optically-thin and thick plasmas.