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We have measured cross sections for elastic and inelastic electron scattering from the deuteron at a scattering angle of 180° and incident electron energies up to 370 MeV. Our elastic scattering results are in agreement with those of Buchanan and Yearian 1 showing disagreement with simple impulse-approximation theory, and for the first time we demonstrate a similar effect in the inelastic scattering. At a scattering angle of 180°, the inelastic cross section near threshold is dominated by the Ml transition from the ground state to the virtual l S state of the deuteron. Our experimental values of the inelastic cross section near threshold are appreciably larger, at high electron energies, than the values derived from impulseapproximation theory. 2 ? 3The apparatus used was essentially similar to that described previously by Rand. 4 The liquid-deuterium target was about 1 cm thick and was confined by 0.001-in. aluminum-alloy foils. Electrons from the Stanford Mark-III linear accelerator were passed through a circular deflecting magnet and through the target. Electrons scattered at 180° traversed the deflecting magnet a second time, bending away from the incident beam, and entered the Mark-HI double-focusing 180° spectrometer. There they were detected by an array of scintillators in a ladder configuration. The momentum acceptance of the spectrometer was 4 % and the over-all momentum resolution was approximately 0.4%. The incident beam was integrated by a secondary emission monitor which was calibrated frequently by passing the beam into a Faraday cup. 4 Table I. Systematic errors. Quantity Error (ft) Target density Target thickness Beam-monitor efficiency Incident-energy calibration Normalization statistics Proton cross section Rms total 4 <1 3 1 2 3 6.3Background scattering was measured with an empty target. At the highest energy used, as many as 50 % of the counts at the top of the elastic peak of the scattered-electron spectrum were background events. To determine the absolute efficiency of the counting system we measured the elastic scattering from a liquidhydrogen target and used the best-fit proton form factors given by Hughes et al. 5 Estimated systematic errors, totaling 6.3%, are listed in Table I.The spectrum of electrons scattered from deuterium at an incident energy of 325 MeV is shown in Fig. 1. Background events have been subtracted. The elastic peak is seen at an electron momentum of 241.3 MeV/c along with the peak due to the excitation of the virtual X S state at 239 MeV/c. The results of a preliminary analysis are also indicated.The theoretical elastic cross section was calculated 1 from impulse-approximation theory using the Partovi model of the deuteron 6 with 7% D state. No meson-exchange diagrams were included. The elastic peak was predicted from the theoretical cross section by folding a 5 function at the proper electron momentum with the momentum resolution function cal-

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