History

When CIOp was created in 1977, investigations of spontaneous spectroscopy and laser were centered on studies of molecular nitrogen and noble gases. The N2 laser was used as an intense source of ultraviolet emission (337,1 nm) and had possibilities for the study in time and frequency of its radiation in the bands of the near infrared. The main research was carried out with a pulsed molecular nitrogen laser refrigerated at liquid air temperature, employing already known technologies but with the support of a high resolution spectrograph having the possibility of being converted into a monochromator with detection by means of lead sulfide detectors, photomultipliers, oscilloscopes, etc.

Besides using Xe as a basis, the laser was employed as generator of stimulated emission in the blue-green zone and the tube as light source, generating rich-in-lines spectra of the first ions of the gas. Our research on Xe laser shows how a proper employment of spectroscopic techniques can solve problems and contribute to generate new research works in the same subject. As in our methodology the analysis of spontaneous radiation was systematic, the study of the measurements gave as a result the detection of about 2000 spectral lines that did not correlate with the existent bibliography and in some cases, showed the correspondence with laser lines having unknown assignments.

Later work consisted of the analysis of data obtained from an spectral source, where a capacitor bank discharged by "quick switches" through a tube containing this noble gas or others like Ne, Ar, Kr at low pressure. The radiation generates in this way is received at the plate holder of a great-dispersion spectrograph. The obtained records are measured by comparison with that of thorium 232, in the photoelectric comparator at the Facultad de Ciencias Astronómicas y Geofísicas de la Universidad Nacional de La Plata (UNLP)., and final data are managed by proper methods to reach the determination of the atomic structure of studied spectra.

Among this general sequence of works, we must also mention those oriented to the study of the discharge parameters, the attainment of spectra by varying the excitation energy of the discharge to be able to assign the ionization state of each transition and to prepare spectroscopy tables. The employment of theoretical calculations programs for the diagonalization of energy matrices and for the attainment of other type of atomic parameters, which allows a better interpretation of experimental results, were also used.

Since 1984, the CIOp has had a spectrograph for working in the vacuum ultraviolet zone of the electromagnetic spectrum, donated by Lund Universitet, Sweden, with which we have maintained a strong scientific relationship on atomic spectroscopy subjects since several years. This instrument has allowed the CIOp to begin the study on ionized noble gases in the V.U.V. zone, which is of interest in astrophysics subjects and in V.U.V. and X-ray lasers

Appart from this instrument, the CIOp has two spectrographs to cover the U.V. visible and near IR zones of the electromagnetic spectrum. One of them, a Shimadzu, belongs to the Universidad Nacional de La Plata, and another one, Hilger Watts, that belongs to the Universidad Nacional de Córdoba, Argentina. Another Hilger Watts instrument belonging to the Universidad Nacional de Tucumán, Argentina, was transferred to CIOp, through an agreement like the previous ones.

All this equipment allows studies on a wide zone of the electromagnetic spectrum by photographic means, from 30 to 1200 nm approximately. Employing electronic detection, the zone can be widened up to wavelengths of several microns. Lately, new detection techniques including linear diode arrays, modern monocromators and CCD cameras, have been used.

Recently, another kind of techniques was performed in our group, the Laser Induced Breakdown Spectroscopy (LIBS). This process involves high-power laser beam focused onto a sample surface or gas producing a ionized plasma and excited elemental components. These spectra are recording in a monochromator with an ICCD camera wich allows to record the temporal evolution of the spectra lines.

It is worth mentioning that all these works briefly described here have resulted in dozen of doctoral theses, some in course at present, and an important number of pregraduate theses. Furthermore we maintain close interinstitutional relations with other groups working on similar subjects, in our country and abroad, especially with the groups of plasma and optical spectroscopy in the universities of Tandil, Rosario, and Mar del Plata, Argentina; and the University of Lund, Sweden, the University of Campinas, and the Universidad Federal Fluminense, Río de Janeiro, Brazil. These include the interchange of scientific material, trips and visits of scientists and students for courses and/or joint works, and the publication of the results in specialized journals.

Finally, data produced in our group about Argon were reported by the NIST, USA, and three compilations about noble gases were also published by the NIST, including the Krypton material J. Phys. Chem Ref. Data 20, 859-915, 1991; J. Phys. Chem Ref. Data 24, 1577-1608, 1995 recently the Xenon data in J. Phys. Chem Ref. Data 33, 765-921, 2004 and also in
http://physics.nist.gov/PhysRefData/ASD/index.html

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