G. Bertuccelli

Spectrum of doubly ionized xenon (Xe III)

The spectrum of doubly ionized xenon has been investigated. The study is based on photographic recordings of xenon spectra in the 490-8900 A range. The number of classified lines has been increased from about 300 to about 1400. The lines have been classified as transitions between 73 even levels belonging to the 5s25p4, 5s25p36p, 4f, 5f and 5s05p6 configurations, and 83 odd levels belonging to the 5s5p5, 5s25p36s, 7s, 5d and 6d configurations. In particular, the classifications include most of the Xe III laser lines. The experimentally observed level structures are compared with the results of Hartree-Fock calculations and least-squares fits. A comparison is also made between the results of the present analysis and the published data on the Xe N4,5 OO Auger spectrum.

Stark Widths and Oscillator Strengths of Xe III Lines (Part II)

Stark widths and relative oscillator strengths were measured for more than 130 Xe III spectral lines emitted in a pulsed capillary discharge. As usual, these parameters become attainable once the deconvolution of line profiles is performed. In particular, 4f?6d, 5d?4f, 5d?6p, 6p?6d, 6p?7s and 6s?4f Xe III transitions have been considered. Extensive configuration interaction (CI) along with least-squares fitted atomic parameters were combined in Cowan code calculations, in order to check the quality of agreement with experimental f-values. Comparisons alike, drawn between experimental Stark widths and Griems semiempirical approach, guarantee an agreement within a factor of two for the whole of the lines, given a proper choice of the Gaunt factor for each single transition.

Stark widths and oscillator strengths of Xe III lines

In order to test the reliability of the Configuration Interaction (CI) method to predict the atomic parameters viz oscillator strengths of complex ions, we measured the profiles of forth (40) strong 6s-6p transitions of Xe III emitted by a pulsed capillary discharge. After deconvoluting the experimental shapes, Stark widths and relative oscillator strengths were obtained. When Least Square Fitted parameters were used in addition to extensive CI (CI + LSF), the agreement between theory and experiment for the gfs is within a factor two for the whole of the lines. Concerning the widths, the semiempirical approach provides values also within a factor two when the Gaunt factor is taken to be g(x) ~ 0.30.

Line shifts of singly ionized xenon in high current pinched discharges

Abstract A study of Xe II line shifts originating in a discharge tube crossed by a high current, generally employed for producing laser action, is presented. By using a simple collisional model, our analysis shows that such shifts can be assigned to the microscopic Stark effect. The values of density and electron temperature, necessary for estimating collision parameters, have been determined by Papayoanou et al. in an independent series of measures under experimental conditions similar to our own.

Optical transition probabilities for lines obtained from pulsed sources

A simple and fast method for the measurements of transition probabilities for lines obtained from pulsed sources is presented. Measuring the linewidth and peak intensities transformed in an internal absolute scale, relative transition probabilities are obtained from a simple relation. The method is useful only for lines with Lorentzian or Voigt type profiles, but many transitions are of this form. For testing the method, 6s‐6p Xe II transitions were selected since several works exist for comparison.

Experimental stark widths of xenon II spectral lines

Stark widths of many prominent 6s-6p and 5d-6p transitions have been measured and compared with theoretical results. A high current pinched discharge was used as a spectroscopic source. Electron density and temperature were estimated in 2.65 × 1022m−3 and 1.45 × 104 K respectively. Experimental Stark widths agree well with previous theoretical results. Our data are compared with those of other authors concerning to the homologous ions Ne II, Ar II, Kr II and Xe II.

RADIATIVE MECHANISMS IN LASER-PRODUCED PLASMAS IN Xe

Abstract In the present paper the LPP in Xenon at nearly atmospheric pressure is studied by frequency as well as temporal resolved spectroscopy. Experimental evidence confirms that the radiative recombination in the aftermath of the laser pulse, is the main mechanism by which the plasma dissipates its energy. It is also evident that the plasma observed is heated after the laser pulse ends, by a radiative wave evolving from the laser spot which also provides electrons. The evidence is supported by a careful analysis of the temporal evolution of ionized species, by the temporal evolution of the spectral shifts of the line spectrum and its spectral width, and by a careful analysis of the continuum emitted after the line spectrum in the plasma during the initial time-stage.

Photorecombination to excited states of Xe in laser produced plasmas

Abstract In the present work, we report the frequency spectra of the continuum generated in a laser produced plasma of Xe, in the region 3000–5800 A. From these studies it can be concluded that we have identified the photorecombination thresholds (radiative recombination, RR) to the excited levels of Xe I and Xe II and some autoionizing resonances nl−El′ transitions where with nl we label bound levels and with El′ auto-ionizing levels are indicated.

Experimental and numerical study of a pulsed cold discharge

Pulsed-cold capillary discharges dominated by electron collisions are very useful for obtaining basic atomic data; furthermore laser action from several times ionized noble gases have been found using this type of discharge. In this work an experimental and numerical study is made such that the temporal behavior of the different ions and the electron density and temperature are in accordance with the experiments within 10-20%.

Temperature and electron density gradient in Xe laser produced plasmas, by spectral analysis

Abstract We have performed a spectroscopic analysis on laser produced plasmas in Xe at intermediates pressures (less than 1 atm), resolved both spectrally and temporally, also discriminating different regions of the plasma. This is produced by tightly focusing the radiation of a Q-switched Nd : YAG laser on a cell equipped with an observation window at right angles with respect to the laser. Our results confirm that there is a gradient in electron density in the plasma ball formed by the laser. This gradient almost defines at least two regions, an outer layer of higher electron number density, and an inner core of lower electron number density. The electron temperature gradient has the same sign. These conclusions are supported by evidence taken using the spectral results mentioned above.