On the line shift and oscillator strength of Xe II lines in the spectra of HnMn stars

Aims. The ultimate goal that has motivated this work is to achieve realistic oscillator strength (gf) values to find reliable values of stellar abundances. We aim to compare the gf valúes of Xe ii lines found with different theoretical and experimental methods. Methods. We have undertaken calculations using the quasirelativistic and relativistic Hartree-Fock methods. Then we compare these results with those previously obtained from UVES spectra of HgMn stars. Results. 1) Our theoretical gf values are more realistic than those previously obtained for most lines. When we consider only unblended, isolated, relatively noise-free lines, however, our theoretical gf values and Yuce's stellar values differ little from each other. 2) In a discussion of the origin of the previously observed discrepancy between the wavelengths of Xe ii lines deducted from stellar spectra and those published by National Institute of Standards and Technology (NIST), we conclude that stellar wavelengths could be considered the standard wavelengths whenever the densities in stellar atmospheres are smaller than 1 × 1016 part. cm-3.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Asignación iónica de líneas del Xe IV

The Xe IV spectrum between 2280 and 6100 A emitted by a new model of a non conventional spectroscopic «ource, has been studied. Si* hundred and «ixty «even lines has been assigned to this ion by employing the conventional method of energy variation, and the characteristic form of the spectral lines resulting from this type of spectral lamp has been particularly considered.El espectro del Xe IV entre 2280 y 6100 A emitido por un nuevo modelo de fuente espectroscópica no-convencional, ha sido estudiado. Seiscientas sesenta y siete líneas han sido asignadas a este ion, empleando el método convencional de variación de energía, y ha sido particularmente considerada la forma característica de las líneas espectrales que resultan de este tipo de fuente espectral.Facultad de Ingenierí

Enhancement of photoacoustic detection of inhomogeneities in polymers

We report a series of experiments on laser pulsed photoacoustic excitationin turbid polymer samples addressed to evaluate the sound speed in the samples and the presence of inhomogeneities in the bulk. We describe a system which allows the direct measurement of the speed of the detected waves by engraving the surface of the piece under study with a fiduciary pattern of black lines. We also describe how this pattern helps to enhance the sensitivity for the detection of an inhomogeneity in the bulk. These two facts are useful for studies in soft matter systems including, perhaps, biological samples. We have performed an experimental analysis on Grilon(R) samples in different situations and we show the limitations of the method.Comment: 8 pages, 7 figure

On the line shift and oscillator strength of Xe II lines in the spectra of HnMn stars

Aims. The ultimate goal that has motivated this work is to achieve realistic oscillator strength (gf) values to find reliable values of stellar abundances. We aim to compare the gf valúes of Xe ii lines found with different theoretical and experimental methods. Methods. We have undertaken calculations using the quasirelativistic and relativistic Hartree-Fock methods. Then we compare these results with those previously obtained from UVES spectra of HgMn stars. Results. 1) Our theoretical gf values are more realistic than those previously obtained for most lines. When we consider only unblended, isolated, relatively noise-free lines, however, our theoretical gf values and Yuce's stellar values differ little from each other. 2) In a discussion of the origin of the previously observed discrepancy between the wavelengths of Xe ii lines deducted from stellar spectra and those published by National Institute of Standards and Technology (NIST), we conclude that stellar wavelengths could be considered the standard wavelengths whenever the densities in stellar atmospheres are smaller than 1 × 1016 part. cm-3.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Enhancement of photoacoustic detection of inhomogeneities in polymers

We report a series of experiments on laser pulsed photoacoustic excitation in turbid polymer samples addressed to evaluate the sound speed in the samples and the presence of inhomogeneities in the bulk. We describe a system which allows the direct measurement of the speed of the detected waves by engraving the surface of the piece under study with a fiduciary pattern of black lines. We also describe how this pattern helps to enhance the sensitivity for the detection of an inhomogeneity in the bulk. These two facts are useful for studies in soft matter systems including, perhaps, biological samples. We have performed an experimental analysis on Grilon®samples in different situations and we show the limitations of the method.Facultad de Ingenierí

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 Å 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, 4ϕ, 5ϕ 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 N4,5OO Auger spectrumFacultad de Ciencias ExactasCentro de Investigaciones Óptica

Asignación iónica de líneas del Xe IV

The Xe IV spectrum between 2280 and 6100 A emitted by a new model of a non conventional spectroscopic «ource, has been studied. Si* hundred and «ixty «even lines has been assigned to this ion by employing the conventional method of energy variation, and the characteristic form of the spectral lines resulting from this type of spectral lamp has been particularly considered.El espectro del Xe IV entre 2280 y 6100 A emitido por un nuevo modelo de fuente espectroscópica no-convencional, ha sido estudiado. Seiscientas sesenta y siete líneas han sido asignadas a este ion, empleando el método convencional de variación de energía, y ha sido particularmente considerada la forma característica de las líneas espectrales que resultan de este tipo de fuente espectral.Facultad de Ingenierí

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 Å 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, 4ϕ, 5ϕ 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 N4,5OO Auger spectrumFacultad de Ciencias ExactasCentro de Investigaciones Óptica

Enhancement of photoacoustic detection of inhomogeneities in polymers

We report a series of experiments on laser pulsed photoacoustic excitation in turbid polymer samples addressed to evaluate the sound speed in the samples and the presence of inhomogeneities in the bulk. We describe a system which allows the direct measurement of the speed of the detected waves by engraving the surface of the piece under study with a fiduciary pattern of black lines. We also describe how this pattern helps to enhance the sensitivity for the detection of an inhomogeneity in the bulk. These two facts are useful for studies in soft matter systems including, perhaps, biological samples. We have performed an experimental analysis on Grilon®samples in different situations and we show the limitations of the method.Facultad de Ingenierí

Evaluation of self-absorption of manganese emission lines in laser induced breakdown spectroscopy measurements

This paper is part o f a more general study aimed to the determination o f the best experimental procedures for reliable quantitative measurements o f F e-M n alloys by LIBS. In this work, attention is pointed on the self-absorption processes, whose effect deeply influences the LIBS measurements, reflecting in non-linear calibration curves. The effect o f self-absorption on the line intensity can be quantified by defining a self absorption coefficient, that measures the deviation o f the line intensity from the linear extrapolation o f the curve o f growth in the optically thin regime. The authors demonstrated in a previous paper that self absorption coefficients could be calculated once the electron density o f the plasma is known and the Stark coefficients o f the lines are available. However, when the Stark coefficients o f the lines o f interest are not known, a different approach is needed. In this work a new method for evaluation o f self absorption coefficients in LIBS measurements is presented, which does not require the knowledge o f Stark coefficients. In order to understand the basic principles and setting out the theoretical tools that w ill be used for the analysis o f the alloys, a preliminary study was done on pure Mn; LIBS spectra were acquired in different experimental conditions, at different laser energies and different delays after the laser irradiation o f the sample. Moreover, collinear double pulse measurements were also performed. Analytical relations were derived and experimental procedures devised for evaluation o f the self absorption coefficients o f several Mn lines, which are important for characterization and control o f the experimental conditions in which the analysis is performed.Facultad de Ingenierí