OPO-pulsed CRDS of the visible collision induced absorption bands of oxygen at low temperature

Collision induced absorption (CIA) bands in molecular oxygen, at 630 and 577 nm, were measured at low temperatures, down to 132 K. Besides providing confirmation of previous room temperature data, and new information about the temperature dependence of CIA bands, these measurements demonstrate the performance of cavity ring down spectroscopy in a rather unusual configuration. The cavity ring down spectroscopy (CRDS) setup includes a broadly tunable commercial pulsed optically pumped oscillator (OPO) laser coupled with a ring down cell, a section of which can be cooled down to liquid nitrogen temperature. In addition, a spectrograph is used as a wavelength-selective element at the cavity output, before measuring the ring down signal. This was needed given the broad OPO lineshape and the coexistence of other wavelengths generated by the OPO system.