A thermooptical technique is described for measuring the absorptivity spectrum of liquids using incoherent light. This technique is an extension of one previously used to measure absorptivity using coherent light, which was therefore limited to specific laser wavelengths. Absorptivities as small as 2 × 10−5 cm−1 have been measured with 2–3 mW of optical power. The absorptivity spectrum of chlorobenzene is characterized by lines due to overtones of C-H vibration in the infrared with low loss valleys in between. Measurements of carbon tetrachloride showed no measurable absorptivity (i.e., less than 2 × 10−5 cm−1) between 5600 Å and 10,600 Å.
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