Momentum-transfer cross section for electron-helium collisions in the range 4-12 eV

Drift velocities of electrons in helium at 293 K have been measured in the range $2.5\le \frac{E}{N}\le 7.0$ Td (1 Td = ${10}^{-17\mathrm{}}$ V/${\mathrm{cm}}^2$), and analyzed to determine the momentum-transfer cross section between 4 and 12 eV. The estimated error bounds on the cross section are ±3% in the range $4\le \epsilon \le 7$ eV and ±5% in the range $7<\mathrm{}\epsilon \le 12$ eV. The implications of the new result to the problem of determining standard cross sections for electron-helium scattering below the first excitation threshold are discussed.