Cross sections for 5D→7S transfer in Rb, induced by collisions with He, Ar atoms, and H2 molecules, respectively, are determined by using methods of atomic fluorescence in a glass fluorescence cell. The resulting fluorescence includes a direct component arising from the optically excited state and a sensitized component due to the collisionally populated state. Measurement of relative intensities of the two components in relation with different quenching gas pressures yieldes the cross sections of σ(5D-7S) of (1.2±0.3)×10-17 cm2, (1.3±0.3)×10-18 cm2, and(8.3±2.1)×10-17cm2 for He, Ar, and H2, respectively. Cross sections for the effective quenching of the 7S state are also determined. The total quenching rate coefficient out of the 7S state is much larger for H2(1.7×10-10cm3·s-1) than for He and Ar. And the coefficient corresponds to the reaction and nonreactive energy transfer. We detenmine the cross section of (1.0±0.4)×10-16cm2 for reaction of Rb (7S) with H2 by experiment. And the cross section of (7.1±2.9)×10-17cm2 for reaction of Rb (5D) with H2 is obtained. The relative reactivity with H2 is in an order of Rb (7S)＞Rb (5D)