- The optical absorption coefficient of a sea water sample was measured at 590 nm by the pulsed photothermal deflection technique. The absorption of the sea water sample was 1.22 x 10-3 cm-1. Corresponding measurements on samples from a standard source of distilled water give an absorption coefficient of 6.44 x 10-4 cm-1. Simple calculations are shown for the thermal gradients and probe beam deflections seen in these types of studies. 1986 SPIE.