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The energy dependence of the giant dipole resonance built on the isobaric analog state was measured in pion-induced double charge exchange on 13 C at incident pion energies of 140-295 MeV. The cross section increases with energy. The excitation function has a typical non-spin-flip signature, expected from simple considerations and verified by sequential model calculations. Three narrower previously reported low-lying states in l3 0 (E x =3.\, 4.5, and 6.1 MeV) exhibit a spin-flip signature and may correspond to the giant Gamow-Teller strength built on the isobaric analog state.PACS numbers: 25.80. Gn, 24.30.Cz, 24.30.Gd, 27.20.+n Several experiments have been carried out at the Los Alamos Meson Physics Facility (LAMPF) to study the properties of double giant resonances in nuclei. Two such exotic vibrational nuclear modes have been observed by these studies: the giant dipole resonance built on the isobaric analog state (|GDR<8>IAS)) [1] and the double giant dipole resonance (|GDR<8>GDR)) [2]. These resonances have been measured recently on a wide range of nuclei. The first is observable only in the (n + ,n~) AT Z = -2 double-charge-exchange (DCX) reaction and was found to be a general feature of all nuclei with TV -Z> 1. The latter is observed in both the (/r + ,/r~) and (K~ ,K + ) DCX modes and is a general collective feature of all nuclei [3]. However, all previous data have been measured at a single pion beam energy of 295 MeV [4,5]. The present work is the first measurement of the energy dependence of double resonances in nuclei excited by DCX. The main object of this Letter is to present the first data for the energy dependence of the cross section of the giant dipole resonance built on the isobaric analog state in the 13 C(;r + ,/r~) 13 0 reaction, and to shed more light on the exact mechanism in which a double resonance state is excited. The excitation of multiphonon states also becomes a very likely process in relativistic heavy ion reactions, where a direct identification of the double giant dipole resonance has been reported recently [61.The measurements were performed at the energetic pion channel and spectrometer (EPICS) at LAMPF with the standard pion double-charge-exchange setup [7]. The isotopic purity and areal density of the 13 C target were 90% and 0.425 g/cm 2 . Measurements were taken at a constant momentum transfer that corresponds to the peak cross section of the |GDR®IAS> angular distribution at five different energies ranging between 140 and 295 MeV. Electrons were eliminated using an isobutane velocitythreshold Cherenkov detector in the focal plane. A scintillator placed behind a series of aluminum and graphite wedges was used to veto muon events [8]. The remaining background was pions resulting from continuum DCX in the target.The acceptance of the spectrometer was measured with a 12 C target using inelastic scattering to the 4.44-MeV state at an energy 7^ = 180 MeV and a scattering angle of 35°, which corresponds to the peak cross section. The spectrometer field was varied to move the...