Knowledge Bank

Phase Shift Cavity Ring Down (PS-CRD) spectroscopy was used for the detection of $(v=0\to 6)$ C-H vibrational transition of deuterated methanes and the $(v=0\to 5)$ transition of HD at room temperature. A continuous wave dye laser in the wavelength range from 600 to 650nm and with a $0.5cm-1$ resolution was electro-optically modulated, and passed through an optical cavity. The change in the phase angle of the modulated laser beam after passing through the cavity was recorded as a function of the wavelength. Absolute cross sections were obtained.