The scattering of slow neutrons by ortho - and para -hydrogen

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Abstract
The neutron velocity selector of the Cavendish Laboratory has been used to measure the scattering cross-sections of ortho- and para-hydrogen for slow neutrons. The triplet and singlet scattering amplitudes of the neutron-proton interaction may be deduced from these cross-sections. The values obtained are at = (0·537 ± 0·004) x 10-12 cm, as = -(2·373 ±0·007) x 10-12 cm, where at and as are the triplet and singlet scattering amplitudes respectively. The values of the coherent scattering amplitude ƒ = 2(3/4a+1/4a), and of the free proton cross-section σƒ= 4π(3/4a2t + 1/4a2s given by the above values of at and as, are ƒ = -(0·380 ± 0·005) x 10-12 cm, σƒ= (20·41 ± 0·14) x 10-24 cm2.