Time-dependent behavior of radical cation in n-dodecane in the presence of cation scavenger at high concentration was measured by picosecond pulse radiolysis. The initial yields decreased with the increase of scavenger concentrations ranging from 0.05 to 4 M. This reduction could not be explained by a first-order rate constant. To solve this discrepancy, we propose an adjacent effect of solute molecules and examined it by a statistical model and Monte Carlo simulation. The relationship with the static quenching model in the photolysis was also discussed. The calculation results showed good agreement with the experimental data.