  Following precise experimental studies at the Duke Free-Electron Laser
Laboratory, we discuss photodisintegration of deuterons with 100% linearly
polarized photons using a model independent theoretical approach taking
together $M1$ and $E1$ amplitudes simultaneously. The isoscalar $M1_s$
contribution is also taken exactly into account. From the existing experimental
measurement on doubly polarized thermal neutron capture, it is seen that the
isoscalar $M1_s$ contribution could be of the same order of magnitude as the
experimentally measured cross sections at energies relevant to Big Bang
Nucleosynthesis (BBN). Therefore appropriate measurements on deuteron
photodisintegration are suggested to empirically determine the $M1_s$
contribution at astrophysical energies.
