The energy gap dependence of the charge recombination (CR) rate constant (k(CR)) Of geminate ion pairs produced by exciting the ground state charge transfer complexes adsorbed on the porous glass was investigated by means of picosecond laser photolysis. The same energy gap dependence of k(CR) as observed in polar solutions by Mataga et al. was also found in the adsorbed systems. Evidently, the present result indicates that not the polar solvent dynamic motions but the intramolecular high-frequency quantum modes in the ion pair predominate in the CR process of these ion pairs. The dielectric constant experienced by the ion pairs on the porous glass was estimated to be ca. 4-5.