Angular Correlation Studies Research Articles

Parity of the Neutral Pion

A study of certain angular correlations in the decay pi /sup 0/ yields 2e /sup +/ + 2e /sup -/ is given. A total of 79 events of pi /sup 0/ production in the captive reaction pi /sup -/ + p yields pi /sup 0/ + n are analyzed. The effective frequency distribution was found to be -0.75 plus or minus 0.42 by experiment and plus or minus 0.48 theoretically, where the plus and minus sign refer to even and odd parity, respectively. It is concluded that the neutral pion is pseudoscalar. (C.J. G.)

ZERO SPIN OF THE 1265-KEV STATE IN Pt194

Angular correlation studies in Ir-194 indicate that the third excited state of Pt-194 has zero spin and presumably, even parity. (C.J.G.)

The Y89 (n, γ) Y90 reaction

The thermal neutron capture gamma rays from the Y89(n, γ)Y90 reaction were investigated in the energy region between 0.18 and 7.0 MeV with a pair spectrometer, a flat crystal spectrometer, and an angular correlation arrangement using two sodium iodide crystals. The prominent gamma rays in the spectrum, which is unusually simple for a nucleus of this mass number, can be fitted to a level diagram for Y90 with levels at 0.2024±0.0003, 0.247±0.002, 0.7767±0.0002, 1.215±0.002 and 2.741±0.012 MeV. Angular correlation studies between cascading gamma rays, with certain assumptions based on the gamma ray intensities, lead to tentative assignments of 2+ and 3− for the levels at 0.7767 and 0.2024 MeV respectively. The neutron binding energy of Y90 is found to be 6.849±0.009 MeV. The observed level scheme is compared with shell model predictions.

Beta-Gamma Correlations with Resonance Fluorescence

The study of beta-gamma angular correlations, with resonance fluorescence of the gamma ray, is proposed as a means of obtaining important information on the beta-decay coupling constants. The effect is calculated for an allowed beta transition followed by a gamma transition of arbitrary multipolarity. As an example, detailed numerical results are given for ${\mathrm{Ne}}^{23}$.

Effect of distribution of nuclear charge on angular correlation in beta-decay

The β— ν and β— γ angular correlation has been computed with consideration of finite electron wavelength for the cases of uniform volume and surface nuclear charge distributions. The calculations were carried out for linear combinations of various forms of beta decay interactions. It is shown that for transitions of first degree of forbiddenness the calculations yield results which perceptibly differ from those of existing approximate calculations. In some cases the difference was as high as 50%. The problem of choosing a nucleus which is most suitable for β— γ angular correlation studies is discussed. A comparison of the theory with experiment is made for the Tm 170 nucleus.

Nuclear Energy Levels ofTl203

Using scintillation spectrometry and coincidence counting techniques, ${\mathrm{Tl}}^{203}$, formed by orbital electron capture in ${\mathrm{Pb}}^{203}$, has been shown to emit gamma rays of energies 280, 403, and 683 kev. The 403- and 280-kev gamma rays were found to be in sequence; the 683-kev gamma ray represents the associated cross-over transition. By energy and conversion coefficient measurements, it has been shown that the same 280\ifmmode\pm\else\textpm\fi{}2 kev level of ${\mathrm{Tl}}^{203}$ is excited in the decay of both ${\mathrm{Hg}}^{203}$ and ${\mathrm{Pb}}^{203}$. A coincidence method for the measurement of the conversion coefficients of the 403-kev gamma rays is described. The $K$-shell conversion coefficient of the 403-kev gamma ray has been measured as 0.076, the $\frac{K}{(L+M)}$ ratio being 3.7. The angular correlation function for the 403-kev---280-kev cascade has the form $W(\ensuremath{\theta})=1\ensuremath{-}(0.152\ifmmode\pm\else\textpm\fi{}0.007){cos}^{2}\ensuremath{\theta}$. For the known multipole mixture of the 280-kev quantum, the correlation measurements indicate the 403-kev transition to be 76 percent $E2$ and 24 percent $M1$. The interference phases of the $E2$ and $M1$ matrices of both transitions are the same in Lloyd's notation. The angular correlation studies and the conversion coefficient measurements indicate the orbitals of the levels of ${\mathrm{Tl}}^{203}$ to be ${d}_{\frac{5}{2}}$, ${d}_{\frac{3}{2}}$, and ${s}_{\frac{1}{2}}$, in order of decreasing excitation energy. The spin of the ground state of ${\mathrm{Pb}}^{203}$ is shown to be $\frac{5}{2}(\ensuremath{-})$.