Giant resonances and bound collective states observed in the scattering of 92.5-MeV electrons from the closed-neutron-shell nucleus Y89 between excitation energies from 2.0 to 55 MeV
Loading...
Authors
Pitthan, R.
Buskirk, F.R.
Dally, E.B.
Shannon, J.O.
Smith, W.H.
Subjects
Advisors
Date of Issue
1977-09
Date
Publisher
Language
Abstract
92.5 MeV electrons were used to study in (89)Y the excitation range between 2 and 55 MeV. Above neutron threshold, broad electric resonances have been seen at 14.0 (63A(-1/3) MeV (E2, vT = 0) and 28 (125A-(1/3) MeV (E2, vT = 1). The total width of the isoscalar E2 resonance is (4.5 +/-0.4) MeV and its strength (56 =/- 6) % energy-weighted sum rule (E2, vT = 0). For the isovector E2 resonance only a minimal value of 7 MeV for the width can be given which is connected with (48 +/- 5)% of the isovector sum rule. The strength of the E1 resonance [T>7(104 =/- 10)% of the Thomas-Reiche-Kuhn sum rule] agrees well with (y,n) measurements, thus giving a check for the accuracy of the evaluating methods employed. A structure around 19-20 MeV, believed to be the T> part of the giant dipole resonance, carries (8 +/- 3)% of the E1 sum rule. In addition to these generally well known states, clustering of E3 strength, (13 +/- 2)% energy-weighted sum rule (E3, vT = 0), was found at 6.75 and 80.5 MeV; the enveloping line shape of these clusters was best described by a Breit-Wigner term. Other concentrations of strength include E3 at 2.6 MeV, (15 +/-3)% energy-weighted sum rule E3, (vT = 0), E2 at 4.0 MeV, (11 +/- 3)% energy-weighted sum rule (E2, vT = 0), and E3 strength at 13.5 MeV. No resonance other than the E1 was found around 17 MeV, thus ruling out in (89)Y the existence of a monopole state with 100% sum rule proposed for (90)Zr from (a,a') and (e,e') measurements. In contrast to heavy nuclei, no resonant 3hw E3 strength could be located.
Type
Article
Description
Series/Report No
Department
Physics and Chemistry
Organization
Naval Postgraduate School (U.S.)
Identifiers
NPS Report Number
Sponsors
Funder
Format
13 p.
Citation
Physical Review C, v. 16, no. 3, September 1977, pp. 970-982
Distribution Statement
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.