The 98 deg differential photoneutron cross section for /sub 4/He has been measured for excitation energies between 22 and 33 MeV with a liquid /sup 4/ He target at its normal boiling point and for excitation energies between 23 and 37 MeV with a /sup 4/He gas target at a pressure of 5l.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 /sup 4/He target may explan the large values for the ratio sigma ( gamma , p)/ sigma ( gamma , n) obtained by comparing photoneutron and photoproton cross sections obtained with targets in different physical states. (auth)

The 98 \ifmmode^\circ\else\textdegree\fi{} differential photoneutron cross section for $^{4}\mathrm{He}$ has been measured for excitation energies between 22 and 33 MeV with a liquid $^{4}\mathrm{He}$ target at its normal boiling point and for excitation energies between 23 and 37 MeV with a $^{4}\mathrm{He}$ 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 $^{4}\mathrm{He}$ target may explain the large values for the ratio $\frac{\ensuremath{\sigma}(\ensuremath{\gamma},p)}{\ensuremath{\sigma}(\ensuremath{\gamma},n)}$ obtained by comparing photoneutron and photoproton cross sections obtained with targets in different physical states.