Optimization of the optothermal detector for absorption spectroscopy in the low pressure range

To use the sensitivity and the measurement accuracy of the optothermal detector (OT) better for linear absorption detection, a theory of the signal behaviour, worth for the most important range of application, is developed and compared with experimental data. By means of the example of CO₂-laser light absorption by ammonia, containing two different nitrogen isotopes, the possibility of correcting measured values to get more exact information of the absorption behaviour is shown. The limits of error, as well as the reproducibility of the measurments could be kept in a range of about 1%.