Angular Distribution Coefficients Research Articles

Angular distribution of de-excitation gamma-rays in Coulomb excitation with large energy loss

The angular distribution coefficients b k Eλ(ξ) and b k Mλ(ξ) of the gamma-rays emitted by nuclei excited by Coulomb excitation are calculated in the limit ξ⪢1 with the use of asymptotic expansions of the Coulomb integrals. These coefficients are expressed as series expansions with ξ − 2 3 as expansion parameter; the expansion coefficients are evaluated numerically. Numerical values of a k πλ(ξ) (b k πλ(ξ)/b 0πλ(ξ)) are presented for 5< ξ<140.

Energy levels in 16N from 15N(n, n) 15N elastic scattering

Elastic 15N(n, n) 15N scattering is studied in the neutron energy range between 1.9 and 3.5 MeV by the recoil particle method. A 15N 2 filled proportional counter is used. The total cross section is measured by integral pulse counting and angular distributions are deduced from pulse-height distributions. The result is presented as a total cross section curve and Legendre polynomial expansion coefficients ( B 0 through B 4) of angular distributions at 50 neutron energies. Analysis is made in terms of levels in 16N in the region between 4.3 and 5.8 MeV excitation. Evidence is found for the 2 broad single-particle states(1p 1/2) −1 ld 3/2 with J π = 1 − and 2 − predicted by the shell model, at an excitation energy of about 5.0 MeV. Six narrower levels are found, spins and parities of which are partly determined.

Mechanisms for the O16(He3, He4)O15 reaction

BS>Excitation curves for the OO/sup 16/(He/sup 3/, alpha )O/sup 15/ and O/sup 16/(He /sup 3;p) F/sup 18/ reactions show pronounced resonance structure in the He/sup 3/ energy range from 2.0 to 3.0 Mev. It has been previously demonstrated that the energy dependenee of the alpha particle angular distribution coefficients in the region of the strongest resonance structure requires interference between compound states with angular momentum 1/2 and 5/2 and like parity at excitations of 10.44 and 10.46 Mev in Ne/sup 19/. Total and partial widths tor both resonances were extracted from the data; the He/sup 3/ partial width of the 1/2 resonance is 67% of the single particle limit. In fitting the expertmental data, it was necessary to include the energy dependence of the resonance parameters. Alpha particle angular distributions measured between resonances indicate a direct interaction mechanism for the reaction. A small, relatively constant direct interaction reaction amplitude and a markedly energy dependent compound system amplitude which is dominant in the vicinity of compound system resonances are suggested by these measurements. An upper limit of 0.8 mu b was established for the He/sup 3/ capture cross section proceeding through the 1/2 resonance. (auth)

Angular Distribution Coefficients for Radiation Scattered by a Spherical Particle*

The fraction of randomly polarized radiation scattered by a spherical particle into a unit solid angle in the direction θ can be represented by the equation f(θ)=14π+14π∑n=1∞anPn(cosθ),where Pn(cosθ) are the Legendre polynomials. Values of the angular distribution coefficients, an, are presented for nonabsorbing spheres with an index of refraction of 1.33 at a series of values of the ratio of circumference to wavelength of 1, 2, 3, 4, 5, 6, 8, 10, 15, 20, 25, and 30. Application of the results is illustrated.

Representation of the Angular Distribution of Radiation Scattered by a Spherical Particle*

Exact expressions have been derived from the Mie equations for the angular distribution coefficients, an, in the equation, f(θ)=14π+14π∑n=1∞anPn (cosθ),proposed by Hartel for the fraction of randomly polarized radiation scattered by a spherical particle into a unit solid angle in the direction θ. The coefficients are functions of the wavelength, particle diameter, and physical properties, and Pn (cosθ) are the Legendre polynomials. This equation is shown to be more convenient in form for tabulation of the scattering properties and for application than the intensity functions used by Mie and most subsequent investigators. Approximate methods for evaluating the coefficients were found to be inaccurate or inconvenient. The exact expressions, although detailed, are suitable for straightforward computation.