THRESHOLD EFFECTS IN NEUTRON ELASTIC SCATTERING

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1963

OSTI ID:4166827

Wells, J T

In an attempt to observe the Wigner cusp phenomenon in neutron elastic scattering near inelastic thresholds, the differential elastic and total cross sections of Li, Fe, Zr, Ba and Ce were measured near the threshold energy for exciting the first excited states of the dominant isotopes of these elements. The energy region investigated extended approximately 300 kev on either side of threshold. The theory of Wigner cusps and energy-averaged'' Wigner cusps is supplemented by a consideration of more general angular momentum situations. Cusp predictions are given in terms of the coefficients for expansion of the cross sections into a series of Legendre polynomials. This form facilitates comparison of theory and experiment. The predicted cusp effect was too small to be observable in Li in the present experiment, and the resonance structure of the cross sections overshadowed the expected cusp effect in Fe. A drop, commencing at inelastic thresholds, was observed in the elastic cross sections of Ce, Ba, and Zr. Analysis of this effect in terms of the theory of energyaveraged'' Wigner cusps yielded good agreement between theory and experiment. This indicates that: the assumptions underlying the theory of energy-averaged cusps are indeed applicable to these nuclei; the amount of direct interaction at these energies (<2 Mev) is small for these target nuclei, otherwise, below threshold effects would be expected; and spins and parities of excited states can be determined in favorable cases by a study of threshold effects. (M.P.G.)

• Research Organization: Originating Research Org. not identified
• NSA Number: NSA-18-000997
• OSTI ID: 4166827
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ANGULAR MOMENTUM
BARIUM
CERIUM
CROSS SECTIONS
DIRECT REACTIONS
ELASTIC SCATTERING
ENERGY LEVELS
EXCITATION
IRON
ISOTOPES
LEGENDRE FUNCTIONS
LEGENDRE POLYNOMIALS
LITHIUM
MATHEMATICS
MEASURED VALUES
MOMENTUM
NEUTRONS
NUCLEAR REACTIONS
PARITY
PHYSICS
RESONANCE
SCATTERING
SPIN
TARGETS
THRESHOLD ENERGY
WIGNER SCATTERING
ZIRCONIUM