We measured the absorption spectrum (340-640 nm) of the purest water available with photothermal deflection spectroscopy. Our spectrum exhibits an absorption minimum in the blue region of the specturm that is deeper than in most previously documented pure-water absorption studies. We attribute this to exceptional sample purity and our techniques's inherent freedom from scattering effects. Because the absorption minimum is significantly lower, our spectrum displays high-order molecular resonance structure not observed in any previous absorption studies to our knowledge. We find the minimum in the absorption specturm of pure water is 0.0062±0.0006 m- 1 at 420 nm and 25°. }
F. M. Sogandares, E. S. Fry, "Absorption spectrum (340- 640 nm) of pure water. I. Photothermal Measurements," Appl. Opt.,36, 8699-8709, (1997).