Observations of small-scale interstellar structure in dense atomic gas

We present high-resolution (R similar to 170,000) Kitt Peak National Observ atory coude feed telescope observations of the interstellar K I lambda 7698 line toward five multiple star systems with saturated Na I components. We compare the K I absorption-line profiles in each of the two (or three) line s of sight in these systems and find significant differences between the si ght lines in three out of the five cases. We infer that the small-scale str ucture traced by previous Na I observations is also present in at least som e of the components with saturated Na I absorption lines, and thus the smal l-scale structures traced by the neutral species are occurring at some leve l in clouds of all column densities. We discuss the implications of that co nclusion and a potential explanation by density inhomogeneities.