2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/171520Experimental observation of Doppler-free signals for weak transitions can be greatly facilitated by an estimate for their expected amplitudes. We derive an analytical model which allows the Doppler-free amplitude to be estimated for small Doppler-free signals. Application of this model to formaldehyde allows the amplitude of experimentally observed Doppler-free signals to be reproduced to within the experimental error.7 pages, 7 figures, 1 table, v2: many small improvements + corrected line assignmentOpticstext