98° Differential Cross Section for the ReactionHe4(γ,n)He

Abstract

The 98' differential photoneutron cross section for 4He has been measured for excitation energies between 22 and 33 MeV with a liquid 'He target at its normal boiling point and for excitation energies between 23 and 37 MeV with a 4He gas target at a pressure of 51.6 bars. The cross-section values obtained with the gas target were approximately a factor of 1.9 greater than those obtained with the liquid target. This apparent dependence of the cross section upon the physical state of the He target may explain the large values for the ratio cr(y, p)/cr(y, n) obtained by comparing photoneutron and photoproton cross sections obtained with targets in different physical states.

Two-body photodisintegration ofHe4with full final state interaction

“…First experiments on the (γ, n) reaction were performed some 50 years ago [1]. In the following 25 years various experimental groups carried out measurements for both the 4 He(γ, p) 3 H and 4 He(γ, n) 3 He reaction channels and the inverse capture reactions [2,3,4,5,6,7,8,9,10,11,12,13,14,15]. Dramatically conflicting results have been obtained as a result of this work.…”