New fundamental equations of state for parahydrogen, orthohydrogen
and normal hydrogen were developed to replace the previous standards (Younglove 1962).
New equations of state have been developed in the Master's Thesis of Jacob Leachman (4) for normal hydrogen, parahydrogen, and orthohydrogen
; these equations will be fully documented elsewhere (5).
Low energy neutrons depolarize rapidly in orthohydrogen
, while those below 15 meV retain their polarization in a parahydrogen target; hence, it is important to ensure that the liquid hydrogen target is prepared and maintained with the very low equilibrium ortho-hydrogen concentration of 0.1 %.