Correlated Neutron-Proton Pairs from the High-Energy Photodisintegration of Helium and Lithium

Abstract

Observations are made on the protons and neutrons simultaneously ejected from helium and lithium by 280 Mev bremsstrahlung. All photoprotons are found to be accompanied by a neutron. The results are interpreted in terms of Levinger's quasideuteron theory of photodisintegration. The results lead to a measurement of the low momentum spectrum in helium and lithium as well as identification of the high-momentum components of the momentum spectrum as due to two-particle interactions.

Angular distributions of protons from bremsstrahlung of maximum energy 400 MeV incident on elements between lithium and gold

“…Any conclusions drawn in these papers have been based on too few data and can presumably be neglected. It must also be pointed out that more recent calculations of the photoproton spectra from quasi-deuterons [1,25,26] do not show "breaks": the discontinuity is completely smeared out by the initial momentum of the n-p pair.…”

“…Lithium has been included in nearly every study of photo-proton emission [1,6,11,13,15]. Most of the data in the early measurements are not readily accessible, since only in rare instances are the crosssections presented in other than graphical form.…”

“…During the last twenty years, a number of papers [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] have dealt with the emission of high-energy protons and correlated neutron-proton pairs from nuclei irradiated with high-energy bremsstrahlung. Although the qualitative features of photo-proton emission are believed to have been established, examination of the literature shows that there are in fact few accurate experimental data available.…”

Photoproduction of high-energy neutrons in thick targets by electrons in the energy range 150 to 270 MeV

“…The results of the investigation of the nuclear photoeffect, which have been described in several publications [4][5][6][7], point out that at photon energies above 150 MeV the (~, rip) process is the dominant absorption process and that in this region the experimental data can be satisfactorily described by the quasi-deuteron model originally proposed by Levinger [8] and improved by other authors [9][10][11].…”

“…The quantities Ewen and Eb merely cause changes in the absolute values. Following Levinger, Barton [5] and Matthews a value of Eb=--10 MeV was used, For Ewen a value of 30 MeV was chosen, which is compatible with the analyses according to the optical model [31], which yield energy-dependent values between 20 and 40 MeV for the real part of the nuclear potential for proton energies between 40 and 120 MeV. Only the high-energy part of the neutron spectrum above 80 MeV was used for the fit, because-as has been mentioned earlier-in this region the (~,, np) process is clearly dominant.…”