Measurement of the absolute intensity of the fifth CH stretching overtone of benzene using cavity ring-down spectroscopy

We present measurements of the absolute absorption intensity of the weak fifth overtone of the CH-stretch vibration of benzene at 16 550 cm−1. By using cavity ring-down spectroscopy, it is possible to obtain directly the absolute value of the oscillator strength of the detected transition (f=(5.9±0.8)×10−11). For this purpose, we had to develop a means of heating the cavity mirrors. The influence of the mirror heating on the measured spectra is discussed.