P. Taras

Spin assignments following heavy-ion induced reactions

Abstract An essentially model-independent method is presented which allows the extraction of spin and mixing ratio values from the measurements of γ-ray excitation functions and angular distributions following heavy-ion induced reactions. The critical assumption is that the initial state observed be fairly well aligned, as has been found to be the case in all heavy-ion induced reactions studied so far. The analysis proceeds from the initial state down the γ-ray cascade to the ground state and takes into account the contribution due to side feeding. The actual form of the magnetic substrate distribution of the initial state is found to be not important although a Gaussian distribution with width σ =1.0–2.0 is used since it appears to have a reasonable physical basis. It is pointed out that the γ-ray angular distribution “typical” of stretched quadrupole transition cascades may also be fitted by dipole-quadrupole mixtures. In the past, this point has been largely ignored in assigning spins to over 300 states in the heavier mass region.

The asymmetry ratio of a compton polarimeter - a computer program

Abstract A computer program has been written to calculate the asymmetry ratio of a Compton polarimeter which consists of two cylindrical NaI(Tl) counters whose axes are parallel to each other. The calculations are in good agreement with the experimental values deduced from the polarization measurements on the gamma rays of 60Ni and 88Sr.

POLARIZATION MEASUREMENTS OF NUCLEAR GAMMA RAYS.

Abstract A computer program has been used to do a systematic study of the asymmetry ratio R , of a Compton polarimeter. The effects of the finite sizes of the crystals that make up such a polarimeter are discussed. Conditions that should optimize the sensitivity of a polarization measurement are also presented.

Interpretation of the isotropic gamma-ray angular distribution for a final state of spin 32

Abstract Values of the spin of the upper state and of the mixing ratio of the decay γ rays consistent with an isotropic angular distribution of the γ rays leading to a final state of spin 3 2 are presented. The usefulness of a linear polarization measurement under these cond conditions is discussed.

Gamma-ray linear-polarization and angular-distribution formulas for mixtures of three multipoles

Abstract Gamma-ray linear-polarization and angular-distribution formulas for mixtures of three multipoles are presented in terms of the phase-defined reduced matrix elements of Rose and Brink. These formulas are applicable to the simple angular distribution as well as to the particle-gamma angular correlation known as Method II of Litherland and Ferguson. In addition, a “recipe” has been worked out for transforming an angular distribution formula into a linear polarization formula in the general case of a γ radiation consisting of an arbitrary number of multipoles.

Analysis of particle-gamma angular correlations and distributions

Abstract Angular distribution curves for a large number of spin sequences are presented. These can be used in the analysis of gamma-ray angular distributions following particle capture reactions and in the analysis of method II of Litherland and Ferguson when m = ± 1 2 . Values of the mixing ratio, for which gamma-ray angular distributions are isotropic, are also given. In addition, the effect of the finite size of the particle counter in particle-gamma correlations is shown to become less important with increasing spin of the initial state in a gamma-ray transition.

ANALYSIS OF LINEAR POLARIZATION MEASUREMENTS OF UNRESOLVED GAMMA RAYS.

Abstract An analytical method which makes it possible to interpret the data from a linear polarization measurement of two unresolved γ-rays is presented. The method is applied to two partially resolved γ-rays in 35 Cl.

Theoretical angular distribution curves for reactions with entrance channel spin 1/2

Abstract Theoretical angular distribution curves have been computed for a number of transitions between levels of spins 1/2 up to 9/2 and levels of spins 1/2 up to 7/2. In each case the entrance channel spin is 1/2.

Versatile method for measuring reaction thresholds and short half-lives

Abstract A computer-controlled system, incorporating a pneumatic beam chopper, has been devised to measure simultaneously and with a high degree of convenience reaction thresholds and half-lives as short as 20 ms.

Determination of the Mixing Ratio in the Decay of the Long — Lived 1.612 MeV Level in 37 Ar

Rosner and Schneid1) have shown that the 36Ar (d, p) 37Ar reaction populates the 1.612 MeV level in 37Arvia ln = 3 stripping. This measurement implies a spin and parity of Jπ = 5/2− or 7/2− for this level. They assigned Jπ = 7/2− using shell-model arguments. Goosman and Kavanagh2) have measured the mean lifetime of this level to be τ = 5.15 ± 0.7 ns, using a recoil — Doppler — shift method. They concluded that the 1.612 MeV level has Jπ = 7/2− on the basis of transition probability arguments. In this paper, we report on the determination of the mixing ratio of the gamma — ray transition from the 1.612 MeV level to the 3/2+ ground state of 37Ar.