Using the optothermal method for molecular beam, infrared spectroscopy, we have measured both the fundamental and first overtone of the acetylenic C-H stretch in CF3 CCH. In the fundamental we observe a spectrum which shows only few perturbations. The majority of lines can be successfully fit to a model assuming an anharmonic coupling of the C-H stretch to a single, near-resonant background state with a coupling matrix element of 0.006 cm-1. We have observed other perturbations in this spectrum, including a state coupled by a weak perpendicular Coriolis interaction. All observed couplings are very weak and local in nature. In the overtone, where the density of background states increases by a factor of 100, we observe a spectrum characteristic of a system in the intermediate case of IVR (intramolecular vibrational energy redistribution). Analysis of the R(0) and P(1) transitions provides a homogeneous IVR lifetime of about 2 ns, which is long compared to lifetimes generally quoted for overtone vibrational relaxation. The root-mean-square coupling matrix element in the overtone is about 0.0008 cm-1. The higher J transitions in the overtone suggest that Coriolis interactions are present in the spectrum. The interpretation of these spectroscopic results in the context of IVR is discussed.