Analytical representations of the dipole spectrum of the ground state of helium are derived. From them are calculated the Verdet constant, the mean excitation energies I and I1 characterizing stopping and straggling of a beam of fast particles absorbed in helium and the leading coefficient C(a, b)/R6 of the long-range interaction between atoms a and b a distance R apart. I is 42.0 ev, I1 is 73 ev, C(He, He) is 1.471 A.U. and C(He, H) is 2.830 A.U.