The vibrational spectrum of 1-butyne in the region of the second overtone of the dropC-H acetylenic stretch, 3v(1), was studied, for the first time, at room temperature by photoacoustic spectroscopy and under jet-cooled conditions by vibrationally mediated photodissociation. The latter resulted in a narrowed H action spectrum enabling observation of a splitting between 3v(1) and a close resonating state. The splitting and the simulation of the spectra contours allowed retrieving time scales for energy redistribution and interaction matrix elements. The low average translational energy extracted from the Doppler profile of the H atom argues against a direct dissociation process. (C) 2004 Elsevier B.V. All rights reserved.