The rate at which molecular oxygen absorbs radiation in the O3(X3&Sgr;g→b1&Sgr;g) transition is calculated using a line-by-line radiative transfer model. This rate is critical to the determination of the population of the O2(b1&Sgr;g) state required for studies of the O2(b1&Sgr;g→X3&Sgr;g) dayglow, the O2(a1Δg→X3&Sgr;g) dayglow, and possibly the rates of oxidation of H2 and N2O. Previous evaluations of this rate (which is sometimes called the g-factor) have significantly overestimated its value. The rate is tabulated as a function of altitude, pressure, and solar zenith angle. ¿ American Geophysical Union 1993