H. L. Clark

Tests of transfer reaction determinations of astrophysical S factors

The {sup 16}O({sup 3}He,d){sup 17}F reaction has been used to determine asymptotic normalization coefficients for transitions to the ground and first excited states of {sup 17}F. The coefficients provide the normalization for the tails of the overlap functions for {sup 17}F{r_arrow}{sup 16}O+p and allow us to calculate the {ital S} factors for {sup 16}O(p,{gamma}){sup 17}F at astrophysical energies. The calculated {ital S} factors are compared to measurements and found to be in very good agreement. This provides a test of this indirect method to determine astrophysical direct capture rates using transfer reactions. In addition, our results yield S(0) for capture to the ground and first excited states in {sup 17}F, without the uncertainty associated with extrapolation from higher energies. {copyright} {ital 1999} {ital The American Physical Society}

Tests of transfer reaction determinations of astrophysical {bold {ital S}} factors

The {sup 16}O({sup 3}He,d){sup 17}F reaction has been used to determine asymptotic normalization coefficients for transitions to the ground and first excited states of {sup 17}F. The coefficients provide the normalization for the tails of the overlap functions for {sup 17}F{r_arrow}{sup 16}O+p and allow us to calculate the {ital S} factors for {sup 16}O(p,{gamma}){sup 17}F at astrophysical energies. The calculated {ital S} factors are compared to measurements and found to be in very good agreement. This provides a test of this indirect method to determine astrophysical direct capture rates using transfer reactions. In addition, our results yield S(0) for capture to the ground and first excited states in {sup 17}F, without the uncertainty associated with extrapolation from higher energies. {copyright} {ital 1999} {ital The American Physical Society}

Asymptotic Normalization Coefficients for 13 C + p ! 14 N

The {sup 13}C({sup 14}N,{sup 13}C){sup 14}N proton exchange reaction has been measured at an incident energy of 162 MeV. Angular distributions were obtained for proton transfer to the ground and low-lying excited states in {sup 14}N. Elastic scattering of {sup 14}N on {sup 13}C also was measured out to the rainbow angle region in order to find reliable optical model potentials. Asymptotic normalization coefficients for the system {sup 13}C+p{r_arrow}thinsp{sup 14}N have been found for the ground state and the excited states at 2.313, 3.948, 5.106, and 5.834 MeV in {sup 14}N. These asymptotic normalization coefficients will be used in a determination of the {ital S} factor for {sup 7}Be(p,{gamma}){sup 8}B at solar energies from a measurement of the proton transfer reaction {sup 14}N({sup 7}Be,{sup 8}B){sup 13}C. {copyright} {ital 1998} {ital The American Physical Society}

Isoscalar giant dipole resonance in 90Zr, 116Sn, 144Sm and 208Pb excited by 240 MeV α particle scattering

Abstract The giant resonance regions of 90 Zr, 116 Sn, 144 Sm and 208 Pb were investigated using 240 MeV α particle scattering at small angles including 0°. E1 strengths corresponding to 91±11%, 89±10%, 105±12% and 95±13% of the isoscalar E1 energy-weighted sum rule were identified beteen 18≤E x ≤31 MeV, 16≤E x ≤30 MeV, 15≤E x ≤27 MeV and 15≤E x ≤25 MeV with centroid energies of 24.8±0.4 MeV, 22.5±0.3 MeV, 21.6±0.3 MeV and 19.3±0.3 MeV and rms widths of 3.2±0.2 MeV, 3.5±0.2 MeV, 3.2±0.2 MeV and 2.5±0.2 MeV for 90 Zr, 116 Sn, 144 Sm and 208 Pb, respectively. Parameters obtained for the isoscalar giant monopole resonance, isoscalar giant quadrupole resonance and high energy octupole resonance are in agreement with accepted values.

Compressibility of nuclear matter from the giant monopole resonance

Abstract The E0 strength distribution in 90 Zr, 116 Sn, 144 Sm and 208 Pb have been measured with inelastic scattering of 240 MeV α particles at small angles. The E0 strengths in 116 Sn, 144 Sm and 208 Pb were found to be concentrated in symmetric peaks and centroid of the strength distributions were located at E x = 16.00±07, 15.31±11, and 14.24±11 MeV respectively. In 90 Zr the E0 distribution was found to have a high energy tail extending up to Ex = 25 MeV. The resulting centroid of the E0 strength for 90 Zr is Ex=17.89±20 MeV. These results and the previously reported result for 40 Ca lead to K nm =231±5 MeV by comparing to mecroscopic calculations.

High lyingE0strength in12C

The excitation region in {sup 12}C from 7MeV{lt}E{sub x}{lt}60MeV was studied with inelastic scattering of 240-MeV {alpha} particles at small angles including 0{degree} where E0 strength is enhanced. The strengths of known 0{sup +} states at E{sub x}=7.655MeV and E{sub x}=10.3MeV were obtained and E0 strength was observed to be distributed between E{sub x}=14MeV and E{sub x}=30MeV with a centroid of 21.5{plus_minus}0.4MeV and an rms width of 3.1{plus_minus}0.2MeV containing 14.5{plus_minus}4.0{percent} of the isoscalar E0 energy-weighted sum rule. Angular distributions and strengths of the E{sub x}=4.439MeV2{sup +}, 9.641MeV3{sup {minus}}, and 10.844MeV1{sup {minus}} states were also obtained. {copyright} {ital 1998} {ital The American Physical Society}

Asymptotic normalization coefficients and astrophysical radiative capture reactions

Abstract The differential cross sections for the reactions 9 Be( 10 B, 9 Be) 10 B at an incident 10B energy of 100 MeV and 16 O( 3 He,d) 17 F ∗ (0.495 MeV , 1 2 + ) at an incident 3He energy of 29.75 MeV were measured. By normalizing the theoretical DWBA proton exchange cross sections to the experimental ones, the asymptotic normalization coefficients (ANCs) for the virtual decays 10 B → 9 Be+p and 17 F ∗ (0.495 MeV ) → 16 O+p have been found. These ANCs are used to calculate the S(0)-factors for the direct radiative captures 9 Be + p → 10 B + γ and 16 O + p → 17 F ∗ (0.495 MeV ) + γ .

Isoscalar giant resonance strength in {sup 24}Mg

The giant resonance region from 9 MeV <E{sub x}<60 MeV in {sup 24}Mg has been studied with inelastic scattering of 240-MeV {alpha} particles at small angles, including 0 deg. Isoscalar E0, E1, E2, and E3 strength was identified from 9 MeV <E{sub x}<40 MeV and the effects of differing continua studied.

Giant resonances in {sup 116}Sn from 240 MeV {sup 6}Li scattering

Giant resonances in {sup 116}Sn were measured by inelastic scattering of {sup 6}Li ions at E{sub {sup 6}Li}=240 MeV over the angle range 0 deg. - 6 deg. Isoscalar E0-E3 strength distributions were obtained with a double folding model analysis. A total of 106{sub -11}{sup +27}% of the E0 EWSR was found in the excitation energy range from 8 MeV to 30 MeV with a centroid (m{sub 1}/m{sub 0}) energy 15.39{sub -0.20}{sup +0.35} MeV in agreement with results obtained with {alpha} inelastic scattering.

Giant resonances in {sup 24}Mg and {sup 28}Si from 240 MeV {sup 6}Li scattering

Elastic and inelastic scattering of 240 MeV {sup 6}Li particles from {sup 24}Mg and {sup 28}Si were measured with the MDM spectrometer. Optical potential parameters for {sup 6}Li+{sup 24}Mg and {sup 6}Li+{sup 28}Si scattering systems were obtained by fitting elastic scattering with two different folding model potentials as well as W-S potentials. E0-E3 giant resonance strength distributions for {sup 28}Si and {sup 24}Mg were obtained. E0 strength corresponding to 106{sub -24}{sup +34}% of the EWSR was identified in {sup 24}Mg and 80{sub -20}{sup +35}% was found for {sup 28}Si between E{sub x}=8.0 to 40.0 MeV.