An automated IR spectrometer was constructed on the basis of a pulsed
optical parametric oscillator tunable in the range 1.5-3.7 mu m. An in
terferometric optothermal method with a phase-contrast system for reco
rding the signal was adopted. When the energy of the parametric oscill
ator radiation was 10 mJ, the minimum detectable absorption coefficien
t was alpha similar to 10(-6) cm(-1).