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.

In this paper, we present a review of experimental work on Stark broadening of singly ionized xenon lines. Eighty lines, from close UV to the red region of the spectrum, have been studied. Stark halfwidths were compared with experimental data from the literature and modified semi-empirical calculations. A pulsed arc with 95% of helium and 5% xenon was used as a plasma source for this study. Measured electron densities Ne and temperatures T were in the ranges of 0.2–1.6 × 1023 m−3 and 18 300–25 500 K, respectively.

This work reports a collection of 200 Ar II transition probabilities of lines in the spectral region 360-750 nm for 16 lifetime values, all of them measured in an emission experiment. Relative intensity measurements have been made on a pulsed discharge lamp and the absolute A ki values have been obtained by using data taken from the literature. The electron density, which ranges from 0.2 to 1.0 × 10 23 m −3 in the plasma, has been determined simultaneously by interferometry and from H α -Stark broadening. The Ar II excitation temperature (15 000-27 000 K) has been calculated by a new method which also provides transition probabilities and plasma composition. The high number of measurements has allowed us to properly discuss the plasma equilibrium model. Comparisons have been made with the most recent experimental and theoretical data collections.

Two experiments assessed the degree to which Pavlovian facilitators were interchangeable with instrumental discriminative stimuli (SdS). In Experiment I, rats were trained in a Pavlovian paradigm in which one stimulus (i.e., a facilitator) signaled the reinforcement of another stimulus (i.e., a target). Next, the rats were given instrumental discrimination training in which an s-signaled the reinforcement of barpressing. A transfer test then assessed the capacity of the Pavlovian facilitator to promote barpressing. The results showed that the facilitator promoted significant barpressing, both when it was presented alone and when it was presented in compound with the Sd. Reliable transfer was not obtained with a "pseudofacilitator" control stimulus that, during training, was uninformative about the reinforcement of its target. Experiment 2 showed that a stimulus trained as an instrumental Sdreliably augmented responding to a stimulus previously trained as a target in a Pavlovian facilitation paradigm. A "pseudo-S?" that, during training, was uninformative about the reinforcement ofbarpressing failed to promote such transfer. These results show that Pavlovian facilitators and instrumental SdS are interchangeable to a significant degree, and suggest that facilitators and SdS may act via similar mechanisms.There has been considerable recent interest in Pavlovian procedures in which one stimulus (B) is informative about the relationship between another stimulus (A) and the unconditioned stimulus (US). For instance, Holland (1983) and Rescorla (1985) have studied paradigms in which A is reinforced when preceded by B but nonreinforced when presented alone. Animals given this A-, BA+ treatment commonly respond more to A accompanied by B than to A presented alone. A similar outcome is also obtained when the A-, BA+ treatment is augmented by separate nonreinforced presentations of B (Davidson & Rescorla, 1986;Ross & Holland, 1982). Ross and Holland (1982) have described B as "setting the occasion" for the reinforcement of A. Rescorla (1985) has described B as a "facilitator" of responding to A.These procedures are of interest not only for what they might reveal about Pavlovian conditioning, but also for their relationship to certain instrumental learning paradigms. As Holland (1983) and Rescorla (1985) have pointed out, there is a formal similarity between the B stimulus in these Pavlovian paradigms and the discriminative stimulus (Sd) in instrumental training paradigms. In the Pavlovian paradigms, only the joint occurrence of A with B is followed by reinforcement; neither A nor B alone is reinforced. Similarly, in operant discriminations, only