Spin excitations in /sup 48/Ca and /sup 90/Zr with 319 MeV protons

Technical Report · Wed May 01 04:00:00 EDT 1985

DOI:https://doi.org/10.2172/5599058· OSTI ID:5599058

Nanda, S K

Cross sections, analyzing powers, and spin-flip probabilities have been measured in the low momentum transfer region in the /sup 90/Zr(p vector, p' vector) /sup 90/Zr* reaction at 319 MeV. A rich fine structure is observed for the first time in inelastic proton scattering in the previously proposed M1 giant resonance region. Angular distribution of most of these states are consistent with M1 excitation. The excitation energies of the fine structure states are in good agreement with similar structure seen in electron scattering; however, discrepancies in spin assignments remain. The measured cross section for the entire bump is about 37 +- 10% of the Distorted Wave Impulse Approximation (DWIA) prediction for the M1 strength in /sup 90/Zr with simple wave functions. However, an analysis of the fine structure states reveals about 15% of the strength in the M1 region to be due to narrow El states; another 8% is attributed to M2 strength. The spin-flip measurements for /sup 90/Zr reveal a large spin-flip probability value for the M1 region; good agreement is obtained with DWIA calculations. However, a large cross section for spin excitations distributed uniformly over the excitation energy region from about 7 to 25 MeV is observed for the first time. The spin excitation strength in this giant resonance continuum is found to about 0.80 mb/sr/MeV. Angular distributions for the spin-flip cross sections from 7 to 18 MeV in steps of 2 MeV have been analyzed with low multipole spin excitation calculations in the DWIA framework; the observed spin-flip strength in this region is found to be consistent with spin excitation involving angular momentum transfer of up to two. Finally, cross section, analyzing power, and spin-flip probability data have also been obtained for the 10.23 MeV M1 transition in the /sup 48/Ca(p vector, p' vector)/sup 48/Ca* reaction at 319 MeV. The quenching of M1 strength in /sup 48/Ca relative to theoretical predictions is found to be consistent with previous work.

• Research Organization: Los Alamos National Lab., NM (USA)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 5599058
• Report Number(s): LA-10368-T; ON: DE85015364
• Country of Publication: United States
• Language: English

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73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ANALYZING POWER
ANGULAR DISTRIBUTION
BARYON REACTIONS
CALCIUM 48 TARGET
CHARGED-PARTICLE REACTIONS
CROSS SECTIONS
DATA
DISTRIBUTION
ENERGY RANGE
ENERGY-LEVEL TRANSITIONS
EXPERIMENTAL DATA
FINE STRUCTURE
GIANT RESONANCE
HADRON REACTIONS
IMPULSE APPROXIMATION
INFORMATION
M1-TRANSITIONS
MEV RANGE
MEV RANGE 100-1000
MULTIPOLE TRANSITIONS
NUCLEAR REACTIONS
NUCLEON REACTIONS
NUMERICAL DATA
PROTON REACTIONS
RESONANCE
SPIN FLIP
TARGETS
ZIRCONIUM 90 TARGET