Capture and scattering probabilities for neutrons impinging on thick samples were measured by the Japan Atomic Energy Research Institute Linac time-of-flight spectrometer and were compared with those by Monte Carlo calculation. Sweeping the incident neutron energy, the capture probability shows peaks at resonance energies in the case of a thin sample, whereas it shows dips for a thick sample, i.e., saturation occurs just at resonance energies. This saturation phenomenon is analyzed by Monte Carlo calculation for a distribution of path lengths of incident neutrons in the sample until capture in the sample. The saturation values of capture probability at resonance energies Pco are defined, and their dependence on the resonance parameters Γn/Γ is examined. The relations between Pco and Γn/Γ, with parameters including recoil energy, are obtained by Monte Carlo calculation. The relations are verified by measurement of Pco for many resonances of various Γn/Γ values. With the relation, Γn/Γ can be determined from Pco, which is not sensitive to sample thickness.