Optical pumping of Na atoms with polarized laser radiation tuned to one of the atomic resonance transitions produces a shift in the vapor phase atom-dimer equilibrium densities. The direction of the shift is determined by the polarization of the light. Besides the already known decrease in equilibrium Na2 vapor density resulting from Na atomic orientation produced by circularity polarized D1 light, an increase in Na2 density is produced when the excitation is changed to plane polarized radiation at either the D1 or D2 transition energy. While there are several possible mechanisms for this latter effect, the evidence seems to point toward a reaction between Na (2P1/2 or 2P3/2) atoms and Na (2S1/2) ground state atoms to form dimers in several electronically excited states which then either radiate or follow dark processes to produce additional ground state dimer density. It is now possible to change the gas phase atom-dimer bulk equilibrium composition to favor either products or reactions by a simply changing the laser polarization and power used for the atomic excitation. When optically pumping with circularly polarized D1 radiation, it is also demonstrated that saturation of the ground state Na atomic Zeeman magnetic resonance transition not only reverses the decrease in equilibrium density of Na2, but also produces an increase above the normal thermal value. The magnetic resonance transition can, therefore, be used to control both the direction and extent of the shift in equilibrium composition.