Energy dependence of infrared emission from azulene C–H stretching vibrations

New data are described on the energy dependence of infrared fluorescence (IRF) from the C–H stretch modes (∼3050 cm−1) of vibrationally excited azulene (C10H8). An optoacoustic method was used to measure the absorbed laser energy and determine the number of excited molecules, while time-resolved infrared emission was recorded. The experimental uncertainties of ∼5% are much smaller than in previous work and the agreement between the experiments and the theory for the IRF intensity is excellent for total vibrational energies from 14 000 to 33 000 cm−1.