J.R. Calarco

Observation of monopole strength in the 12C(e, e′p011B reaction

Abstract The location of the giant monopole resonance and, therefore, the compressibility is unknown in light nuclei. The forward-backward (e, e′p) angular correlation asymmetry from 12 C has been measured and found to be very sensitive to monopole strength in the giant dipole resonance region. Similar reactions will, thus, provide a sensitive tool in the search for monopole strength in light nuclei.

Direct and resonant capture observed in the 3H(τ,γ)6 Li reaction

Abstract A direct capture model is used to calculate the 3H(τ, γ)6 Li cross section. The result for the ground-state cross section is in very good agreement with the data. The calculation for the cross section for the first excited state is in good agreement with the shape and angular dependence of the measured cross section at lower energies. Above Eτ=10 MeV a large discrepancy indicates a non-direct contribution. This is interpreted as a resonance in the compound nucleus 6Li with a configuration other than 3 He + 3 H .

Resonant structure observed in the 3He(τ, γ)6Be capture reaction☆

Abstract The 3 He(τ,γ) 6 Be capture reaction has been studied for 3 He bombarding energies from 12 to 27, MeV. Transitions to the first excited state in 6 Be( T = 1, 2 + ) are readily seen. Transitions to the ground state in 6 Be ( T = 1, 0 + ) are very weak and their presence could not be ascertained. The 90° excitation function for these transitions shows a broad maximum centered at E τ = 23 ±1 MeV. This is interpreted as a resonance in the compound nucleus 6 Be at E x = 23.0±0.5 MeV with a configuration other than 3 He+ 3 He. These results are compared with other experimental work as well as with theoretical predictions.

The giant dipole resonance in 16O observed with the polarized proton capture reaction

Abstract The giant E1 resonance of 16 O has been studied with the polarized proton capture reaction 15 N ( p ,γ o ) 16 O . The asymmetry produced in the angular distribution by the proton polarization was large and remarkably constant over the structure of the giant resonance. Combined with unpolarized measurements the polarized results provide additional information on the configuration of the giant E1 resonance in 16 O.

ELECTRIC DIPOLE RADIATION IN 4He OBSERVED WITH THE POLARIZED PROTON CAPTURE REACTION

Publisher Summary This chapter discusses the electric dipole radiation in 4 He observed with the polarized proton capture reaction. The theoretical and experimental work on the 3 Η (p,γ) 4 He reaction and its inverse have established several interesting features. The experimental El cross section exhibits a broad maximum even after allowance is made for kinematical and penetrability factors. By combining the new measurements with the existing angular distribution data for the unpolarized reaction, solutions for the relative phase of the S = 0 and S = 1 photoproton amplitudes can be obtained. The spin direction for protons can be set either up or down by fixing the direction of the electric current through a spin precession solenoid located between the polarized ion source and the tandem. Reversing the spin does not significantly change the magnitude of the proton polarization. At a given energy and angle, a measurement of the γ-ray yield in the capture reaction is made by alternating runs with proton spin up with runs with proton spin down.

GiantE1 resonances inNe20observed with theF19(p→γ0γ1)20Ne reactions

The giant electric dipole resonance built upon the 0/sup +/ ground state of /sup 20/Ne was studied via the /sup 19/F(p-arrow-right,..gamma../sub 0/)/sup 20/Ne reaction. Polarized and unpolarized angular distributions were measured between E/sub x/ = 16.1 and 23.0 MeV (E/sub p/ = 3--10 MeV) and the E1 T-matrix elements extracted. The /sup 1/P, E1 partial wave dominates, but the weaker /sup 3/P (spin flip) term is also resonant. A heuristic doorway state model has been used to fit the pronounced structure in the giant E1 resonance. Data for the giant resonance built on the first excited state as seen in the /sup 19/F(p-arrow-right,..gamma../sub 1/)/sup 20/Ne reaction are presented and discussed. The microscopic, doorway state calculation in a deformed potential of Schmid and Do Dang is in very good agreement with the main features of the results.

Giant E1 resonances in /sup 20/Ne observed with the /sup 19/F(p-arrow-right. gamma. /sub 0/. gamma. /sub 1/) /sup 20/Ne reactions

The giant electric dipole resonance built upon the 0/sup +/ ground state of /sup 20/Ne was studied via the /sup 19/F(p-arrow-right,..gamma../sub 0/)/sup 20/Ne reaction. Polarized and unpolarized angular distributions were measured between E/sub x/ = 16.1 and 23.0 MeV (E/sub p/ = 3--10 MeV) and the E1 T-matrix elements extracted. The /sup 1/P, E1 partial wave dominates, but the weaker /sup 3/P (spin flip) term is also resonant. A heuristic doorway state model has been used to fit the pronounced structure in the giant E1 resonance. Data for the giant resonance built on the first excited state as seen in the /sup 19/F(p-arrow-right,..gamma../sub 1/)/sup 20/Ne reaction are presented and discussed. The microscopic, doorway state calculation in a deformed potential of Schmid and Do Dang is in very good agreement with the main features of the results.

Giant E 1 resonances in Ne 20 observed with the F 19 (p→ γ 0 γ 1 ) 20 Ne reactions

The giant electric dipole resonance built upon the 0/sup +/ ground state of /sup 20/Ne was studied via the /sup 19/F(p-arrow-right,..gamma../sub 0/)/sup 20/Ne reaction. Polarized and unpolarized angular distributions were measured between E/sub x/ = 16.1 and 23.0 MeV (E/sub p/ = 3--10 MeV) and the E1 T-matrix elements extracted. The /sup 1/P, E1 partial wave dominates, but the weaker /sup 3/P (spin flip) term is also resonant. A heuristic doorway state model has been used to fit the pronounced structure in the giant E1 resonance. Data for the giant resonance built on the first excited state as seen in the /sup 19/F(p-arrow-right,..gamma../sub 1/)/sup 20/Ne reaction are presented and discussed. The microscopic, doorway state calculation in a deformed potential of Schmid and Do Dang is in very good agreement with the main features of the results.

Intermediate structure in the giant E1 resonance in the 19F(p, γ0)20Ne reaction☆

Abstract The striking intermediate structure observed in the giant E1 resonance of 20Ne has been studied with the polarized and unpolarized 19F(p, γ0)20Ne reaction. A heuristic model of four intermediate doorway resonances is found to fit the data.

E1 and E2 Strength in 32s Observed with Polarized Proton Capture

The polarized proton capture reaction is a very powerful tool for studying the giant El resonance as well as M1 and E2 strength in nuclei. The reaction matrix elements for radiative capture can be studied thoroughly if not only the angular distributions, σ(θ), but also the analyzing powers, A(θ), of the emitted photons are observed.