J. Phys. B: At. Mol. Opt. Phys. 31 (1998) 1029–1048. Printed in the UK PII: S0953-4075(98)89211-0 Measurement of Stark broadening and shift of singly ionized Ar lines J A Aparicio, M A Gigosos, V R Gonz´ alez, C P´ erez, M I de la Rosa and S Mar Departamento de ´ Optica, Universidad de Valladolid, 47071 Valladolid, Spain Received 13 November 1997 Abstract. 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 2.0 × 10 23 m −3 has been determined interferometrically and, in the case of pure argon plasmas, also spectroscopically from H α - 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. 1. Introduction The importance of atomic parameter measurements in order to understand atomic structure is very often recognized in conferences and meetings dealing with atoms, molecules, astrophysics and plasma diagnostics. In connection with theoretical work, the knowledge of Stark broadening and the shift parameters of spectral lines allows one to evaluate different hypotheses about the energy level arrangement, the influence of configuration interactions and the meaning of the existing regularities among different atoms with similar electronic structure. From the point of view of experimental work, the relationship between these data and the electron density is very useful in plasma diagnostics and therefore, relevant information about stellar and laboratory plasmas can be obtained from them. Most of the papers published in the last 30 years concerning the Stark broadening and shift parameters of Ar II lines are experimental works [1–18], many of them compiled and evaluated by Konjevi´ c and Wiese [19, 20]. We have found only two theoretical calculations [21, 22]. A very quick look at all these data reveals the existence of a wide spread among the experimental values and systematic differences between them and the theoretical values. Also, most of them correspond to spectral lines belonging to transition arrays 4s–4p, 3d–4p and 4s ′ –4p ′ and there is a great lack of information about transitions between higher energy levels. One of the aims of this work is to provide this kind of information. All the results we will show here have been obtained from a pulsed-discharge lamp. This type of plasma source has two important advantages relative to others for this kind of measurement. Firstly, the linewidths and shifts are almost completely due to the Stark effect. Second, it offers the possibility of making measurements at very different plasma conditions and this fact allows one to study the dependences of these atomic parameters on electron density and, in some cases, on temperature. 0953-4075/98/051029+20$19.50 c  1998 IOP Publishing Ltd 1029