PHYSICAL REVIEW LETTERS, vol.100, no.17, 2008 (SCI-Expanded)
Inclusive inelastic electron scattering off the deuteron under 180 degrees has been studied at the S-DALINAC close to the breakup threshold at momentum transfers q=0.27 fm(-1) and 0.74 fm(-1) with good energy resolution sufficient to map in detail the spin flip M1 response, which governs the starting reaction pn -> d gamma of big-bang nucleosynthesis over most of the relevant temperature region. Results from potential model calculations and (for q=0.27 fm(-1)) from pionless nuclear effective field theory are in excellent agreement with the data.