NONLINEAR RESPONSE OF Si DETECTORS FOR LOW-Z IONS.

We report measurements of the relative mean pulse height produced by **1H, **4He, **7Li and **1**6O ions in Si surface barrier detectors. The data are anomalous in that the pulse height for different ions of the same energy (after window and nonionizing losses are subtracted) increase with atomic number, contrary to observations for fission fragments. A simple model invoking a stopping power dependence of the energy required to create an electron-hole pair is consistent with all experimental data, suggesting that the response of Si detectors is nonlinear with particle energy.