Figure 8.7 — Wavelength dependence of water absorption and photodamage to biological samples Figure 8.7 — Wavelength dependence of water absorption and photodamage to biological samples. (a) Absorption coefficient of water αw as a function of the vacuum wavelength λ0. The shaded area represents the visible portion of the spectrum. (b) and (c) show the photodamage to biological material held in optical tweezers as a function of wavelength: (b) percentage of Chinese hamster ovary cells that remain viable after 5 minutes of trapping at 88 mW power (Liang et al., 1996); (c) time after which the rotation rate of the flagella of E. coli bacteria held in an optical tweezers at 100 mW trapping power decreases to 50% the initial rate (Neuman et al., 1999).