We report experimental results of multifrequency ac conductance measurements on radiation-damaged (100) Si-SiO2 interface after the interfacial defect transformation process has taken place. Previous quasi-static capacitance-voltage measurements on such samples have identified two distinct interface trap peaks, one above midgap and the other below midgap. The presence of such a double-peak interface trap distribution has been confirmed by our ac conductance measurements, and excellent quantitative agreement with the capacitance measurements has been achieved. In addition, the ac conductance measurements showed a strong energy dependence of the capture cross sections of interface traps for both electrons (in the upper half of the band gap) and holes (in the lower half of the band gap). The capture cross sections vary systematically by more than an order of magnitude in an energy range of about 200 meV in either half of the band gap, suggesting that there may be a broad distribution of different defect configurations and/or their surrounding environments at the interface after radiation damage. The energy dispersion of the interface trap time constants and surface potential fluctuations are also obtained and used for accurate extraction of the interface trap density from these data.