H. T. Fortune

Measurements of Deuteron Photodisintegration up to 4.0 GeV

The first measurements of the differential cross section for the d(γ,p)n reaction up to 4.0 GeV were performed at the Continuous Electron Beam Accelerator Facility (CEBAF) at Thomas Jefferson Laboratory. We report the cross sections at the proton center-of-mass angles of 36°, 52°, 69°, and 89°. These results are in reasonable agreement with previous measurements at lower energy. The 89° and 69° data show constituent-counting-rule behavior up to 4.0 GeV photon energy. The 52° and 36° data disagree with the counting-rule behavior. The quantum chromodynamics (QCD) model of nuclear reactions involving reduced amplitudes disagrees with the present data.

A study of 26Al by the 25Mg(3He, d) reaction

Abstract In the 25 Mg( 3 He, d) 26 Al reaction, at a bombarding energy of 18.0 MeV, angular distributions were measured for 55 levels below 6.9 MeV in excitation, and l -assignments are made for 44 of them. Spectroscopic strengths are compared with theoretical ones from the Nilsson model and from a naive shell model. New J π information is given for many levels.

Structure of 17Ne ground state

Abstract Consideration of Coulomb energy for the lowest state with A=17, T= 3 2 , allows determination of the s2/d2 mixture in this state. The d2 configuration is found to dominate.

Structure of 14C from 12C(t, p)

Abstract The reaction 12 C(t, p) 14 C has been investigated with an 18 MeV triton beam. Twenty energy levels of 14 C were identified up to 13 MeV excitation. Angular distributions were measured and compared with DWBA calculations. A previously unreported 0 + level at 9.75 MeV was observed; it undoubtedly corresponds to the second predominantly sd shell 0 + state in 14 C. Additional spin and parity assignments have been made in the present work: 9.81 MeV, (1 − ); 10.43 MeV, 2 + ; 10.50 MeV, (3 − ); 10.74 MeV, 4 + ; 11.40 MeV, 1 − ; 11.67 MeV, (1 − ); 11.73 MeV, (5 − ); 12.58 MeV, (2 + , 3 − ); 12.87 MeV. 2 + , 3 − ; and 12.96 MeV, (1 − ); none of which had a definite spin and parity assignment previously. Our results confirm the previous information on the level structure of 14 C below 8.5 MeV. The cross section for the unnatural parity state at 7.34 MeV, J π = 2 − , is well reproduced by a two-step reaction calculation. The results are compared with the predictions of a weak coupling model.

Search for multiparticle-multihole states of 40Ca with the 32S(12C,α) reaction☆

Abstract Levels of 40Ca below Ex = 10 MeV have been populated with the 32S(12C,α) reaction at an incident energy of 30 MeV. States which are thought to be based on 4p-4h and 8p-8h K = 0 configurations were more strongly populated than other low-lying states.

Location of 0+ 4p-2h and 6p-4h configurations in 42Ca☆

Abstract The 38 Ar( 6 Li, d) 42 Ca reaction identifies a 0 + state at E x = 3.30 MeV, with a major fraction of the 4p-2h strength. Relative α-strengths of other 0 + states are comparable to relative (t, p) strengths.

Spectroscopy of 16C

Abstract The 14C(t, p)16C reaction locates five new states in 16C, at excitation energies of 3120 ± 15, 3983 ± 10, 4136 ± 10 and 6109 ± 15 keV, in addition to the g.s. and 1.76 MeV states. The 3.02 and 3.98 MeV states appear to be the second 0+ and 2+ 2p-2h states, respectively. The 4.14 MeV state has Jπ = 4+ and the 6.11 MeV state has Jπ = 2+, 3−, or 4+.

Indication of Δ-hole configurations in 12C(15.11 MeV)

Abstract A strong energy dependent enhancement is seen in inelastic pion scattering from 12 C to the 1 + , T = 1 state at 15.11 MeV, but not to the 1 + , T = 0 state at 12.71 MeV. This enhancement may be interpreted as evidence for the direct excitation of delta-hole (Δ-h) components in the wave function of the T = 1 state. The required Δ-h amplitude is estimated and found to be in agreement with calculations of Bohr and Mottelson.

Multistep processes in the (d, 6Li) reaction

Abstract At 28 MeV, the (d, 6 Li) reaction on A = 4 n targets in the 1p and 2s-1d shells systematically populates unnatural-parity states with large relative cross sections. This results suggests the presence of multistep reaction processes, making questionable the extraction of nuclear-structure information with DWBA.

Systematics of pion double-charge-exchange reactions on T = 0 nuclei

Abstract Pion induced double charge exchange on 12 C, 16 O, 24 Mg, 28 Si, 32 S, and 40 Ca exhibits forward-angle cross sections that vary rapidly with pion energy and fall off roughly as A −4 3 . Angular distributions at 164 MeV appear diffractive for targets of 12 C, 16 O, and 40 Ca.