2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/105260This communication focuses on sensitivity issues - a long-time concern of J. Hall- in the spectroscopic analysis of Extremely Thin Cell of dilute vapor. With these small and often submicrometric slices of vapor, the most uncommon features are the relatively small number of interacting atoms, and the fact that essential results are already obtained in the frame of linear spectroscopy.Proceedings of the John Hall symposium (2005) to appearAtomic Physicstext