Incoherent broad-band cavity-enhanced absorption spectroscopy of azulene in a supersonic jet

The application of incoherent broad-band cavity-enhanced absorption spectroscopy (IBBCEAS) to isolated jet-cooled gas-phase species is demonstrated on basis of the S1 ← S0 transition of azulene in a continuous supersonic expansion. By focusing white light from a high power Xe-lamp into an optically stable resonator, which is intercepted by the supersonic seeded jet, the absorption is measured over a broad spectral range between 17 300 and 20 255 cm−1 with a resolution of ≈4 cm−1. The resolution, which is due to the dispersion of transmitted light by a grating monochromator, is sufficient to monitor the highly congested vibronic structure >3000 cm−1 above the S1,0 origin of azulene. The sensitivity required for this absorption experiment compares well to that of conventional pulsed cavity ring-down measurements.