Atomic transitions for the doubly ionized argon spectrum, Ar III

 

¹F. R. T. Luna, ²F. Bredice, ³G. H. Cavalcanti, and ^1,4A. G. Trigueiros,
¹Instituto de Física "Gleb Wataghin", Universidade Estadual de Campinas,
UNICAMP, 13083-970, Campinas, São Paulo, Brazil
²Centro de Investigaciones Opticas, CIOp,
Casilla de Correo 124,  1900, La Plata, Argentina.
³Instituto de Física, Universidade Federal Fluminense (UFF),
Campus da Praia Vermelha-Gragoatá, 24210-310 Niterói, Rio de Janeiro, Brazil.
⁴Instituto de Química, Universidade do Estado de Rio de Janeiro,
UERJ, 20550-013 Maracanã, Rio de Janeiro, RJ, Brazil.

 

Received 18 October, 1999

 

 

We present new experimental atomic transition values for the atomic emission spectrum of doubly ionized argon, Ar III. In this work we studied 3 s ² 3 p ⁴ — 3 s ² 3 p ³ 3 d, 3 s ² 3 p ⁴ — 3 s ² 3 p ³ 4 s, 3 s ² 3 p ⁴ — 3 s ² 3 p ³ 4 d, 3 s ² 3 p ⁴ — 3 s ² 3 p ³ 5 s, 3 s ² 3 p ³ 4 p, and 3 s ² 3 p ³ 4 p transition arrays and 196 lines were identified as new atomic transitions between levels of these configurations. The experimental data were obtained from a capillary-discharge tube. The identifications are supported by multiconfiguration Hartree-Fock relativistic calculations.

 

 

I Introduction

The ground state configuration of doubly ionized argon, Ar III, is 3s² 3p⁴ with the terms ³P, ¹D,  and ¹S. Ar III belongs to the S I isoelectronic sequence.

A complete tabulation of the Ar III energy levels was made by Moore [1]. Kelly [2] summarized all the wavelengths published in the vacuum ultra violet (VUV) region. Hansen and Persson [3] published a revised and extended analysis of the optical spectrum of Ar III. Lestven-Vaïsse et al. [4] studied the spectrum of Ar III using the technique of recoil ion spectroscopy and some lines of Ar III were published.

The spectra of argon ions have many applications in different fields of physics such as photo-electron spectroscopy, plasma physics, astrophysics, and collision experiments, for example, in connection with the study of charge exchange mechanisms.

The purpose of our work is to present a report of the analysis of the Ar III spectrum that includes 196 new classified lines.

 

II Experiments

The present work is based on photographic recordings of argon in the 280-5000 Å wavelength range. The spectra were obtained at Centro de Investigaciones Opticas, CIOp, using a capillary pulsed discharge. The light source is built with a Pyrex tube, 30 cm long, and with an inner diameter of 0.3 cm. The tube has inner electrodes and is viewed end on. The excitation of the gas is produced by discharging a bank of low-inductance capacitors varying between 2.5 and 100 nF and charged up to 19 kV through the tube.

In the VUV region the radiation was analyzed using a 3 m normal incidence spectrograph with a concave diffraction grating of 1200 l/mm blazed for 1200 Å . The plate factor in the first order is 2.77 Å /mm. Lines of C III and N II [5], O III [6], and lines of Ar III -Ar V [2], were used as internal wavelength standards.

In the visible region the radiation was detected with a 3.4 Ebert plane-grating spectrograph whose plate factor is 5 Å /mm in the first diffraction order. ²³²Th lines [7] were used as wavelength standards.

In both experiments, a rotating prism photoelectric comparator, whose precision is 1 mm, was used to determine the positions of the spectral lines on the plates. The accuracy of the wavelength values is estimated to be ± 0.01 Å in the VUV region, whereas in the 2500-5000 Å region the uncertainty is estimated to be  ± 0.01 Å and ± 0.008 Å in the first and second diffraction orders respectively.  

The experiments are described in more detail elsewhere [8, 9].

 

III Analysis and theoretical interpretation

Transition identifications were guided by theoretical predictions obtained from Cowan's computer code [10]. The theoretical predictions for the energy levels of the configurations were obtained by diagonalizing the energy matrices with appropriate Hartree-Fock relativistic (HFR) values for the energy parameters. The interpretation of configuration level structures was made by a least-squares fit of the parameters to the observed levels. In the calculations we have included the 3s²3p⁴ and 3s²3p³4p odd configurations and the 3s²3p³3d, 3s²3p³4s, 3s²3p³4d, and 3s²3p³5s even configurations.

The energy level values were determined from the observed wavelengths using the program ELCALC [11], in which the individual wavelengths are weighted according to their uncertainties.

The adjusted experimental energy level values were used as input for the program STRANS. This program allows us to calculate the atomic transitions belonging to the Ar III spectrum.

Table 1 shows the 196 identified lines obtained from the combinations of the odd and even configurations cited above. In the first column of the table the intensities of the lines are shown. They are visual estimates of plate blackening. The second and third columns show the observed and calculated wavelength values.

 

Acknowledgements

The authors wish to thank M. Gallardo and J. G. Reyna Almandos for valuable discussions . This work has been supported by Fundacão de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Brazil; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Brazil; Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (CIC), Argentina; and Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina. Computations were carried out at the Prof. John David Rogers Computational Center, UNICAMP.

 

References

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