Measured lifetimes of states in 197Au and a critical comparison with the weak-coupling core-excitation model

The lifetimes of five excited states in ¹⁹⁷Au up to an excitation energy of 885 keV were measured by the recoil-distance method (RDM). These levels were populated by Coulomb excitation using both 90 MeV ²⁰Ne and 120 MeV ³⁵Cl ion beams. The experimentally determined spectroscopy of the low-lying levels $\text{3}\text{2}{}^{\mathrm{+}}$ (ground state) and $\text{1}\text{2}{}^{\mathrm{+}}$, $\text{3}\text{2}{}_2{}^{\mathrm{+}}$, $\text{5}\text{2}{}^{\mathrm{+}}$, and $\text{7}\text{2}{}^{\mathrm{+}}$ at 77.3, 268.8, 278.9, and 547.5 keV excitation energy, respectively, has been critically compared with the detailed predictions of the de-Shalit weak-coupling core-excitation model. When the model is taken to represent the case of a $\text{d}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ proton hole coupled to a ¹⁹⁸Hg core, the model parameters obtained are in accord with the criteria implicit for weak core coupling and, at the same time, are in remarkably good agreement with virtually all measured E2 and M1 transition rates.     

Raman spectroscopic studies of the solid-state polymerization of diacetylenes. I. Thermal polymerization of 1,6-di-p-toluenesulfonyloxy-2,4-hexadiyne

The resonance Raman spectra of polymer chains in partially polymerized crystals of 1,6-di-p-toluenesulfonyloxy-2,4-hexadiyne are reported. The polymer chain distortion is deduced using the results obtained previously for fully polymerized samples under tensile strain. Changes in crystal lattice dimensions both parallel and lateral to the polymer chains are found to be important in interpreting the variations in frequency of the Raman-active vibrational modes. Further evidence is found for the resonant interaction of backbone and side-group vibrations reported previously. This interaction is affected by the lateral dimensional changes and is also sensitive to residual strain fields in the monomer crystals. It is not necessary in the interpretation of the Raman spectra to take any account of changes in polymer chain length during polymerization.     

Improvement of sensitivity in neutron activation analysis by selective absorption of high-intensity low-energy gamma-rays

A counting technique involving selective attenuation of matrix activity by a lead absorber is described. This technique applies to all cases in which it is necessary to detect low-intensity high-energy γ rays in the presence of high-intensity low-energy γ-rays emitted by the matrix. An improvement in sensitivity of several orders of magnitude can be achieved in some cases. The technique was verified for three matrices and the attenuation factors for a 1 cm lead absorber were calculated for all radioisotopes. Criteria for the choice of the most suitable absorber are discussed.     

Cross section of the reaction 6Li(p, γ)7Be

The cross section of the reaction ⁶Li(p, γ)⁷Be has been measured using Ge(Li) γ-ray spectrometers for proton bombarding energies E_p from 200 keV to 1200 keV. At E_p = 800 keV, the total (p, γ) integrated cross section is found to be 3.1 ± 0.4 μb. The cross section adopted from consideration of this and previous measurements is in good agreement with that predicted from the known thermal neutron cross section for ⁶Li(n, γ)⁷Li on the assumption that properties of mirror direct capture reactions can be well described by optical potentials that use the same parmeter values for the two reactions.     

Morphology and structure of heavily deformed single crystals of a polydiacetylene. II. Resonance raman and optical spectroscopy

Resonance Raman and optical spectroscopy have been used to study foils having a metallic appearance which were produced by the hammering or rolling of single crystals of toluene sulfonate diacetylene polymer. The spectroscopic properties of the bulk material in the foils were found to be almost indistinguishable from those of underformed crystals. In contrast, the blue–green surface skin of the foils appeared to consist of intact polymer chains without significant crystalline order.     

Level structure and lifetimes of low-excitation states in 63Cu

The lifetimes of 9 states in ⁶³Cu up to an excitation energy of 2092 keV have been determined by means of the Doppler-shift attenuation method using the ${}^{60}\text{Ni}\text{(α,}\text{p}\text{γ)}$ reaction. A search was made for a suitable set of M1 and E2 single-particle matrix elements for use with shell-model eigenstates throughout the Ni, Cu and Zn isotopes. The theoretical predictions for the level spectroscopy and electromagnetic transitions and static moments in ⁶³Cu are in satisfactory agreement with the experimental findings.     

Persistence vectors and higher moment tensors of polyoxyalkanes

Statistical mechanical averages of vectors and tensors characterizing the spatial configurations of polyoxymethylene (POM) and polyoxyethylene (POE) chains, i.e., the chain vector r connecting the ends of the chain and the tensors formed from this vector, are evaluated in internal reference frames attached to the first two bonds of each chain as functions of its length. Convergences of the persistence vectors a ≡ 〈 r 〉 with chain length to their limits a _∞ are delineated. For POE, the orientation of a _∞ with respect to the X₁ axes (the direction of the first bond) depends markedly on the choice of the initial bond and hence also on the internal frame of reference. Cartesian tensors up to fourth rank formed from the displacement vector ρ = r ? a are evaluated for n = 4–1922 bonds for POM and n = 3–300 bonds for POE. The second moment tensor 〈ρρ^T〉 calculated for POM is nearly cylindrically symmetric about the axis perpendicular to the plane of the first two bonds. Corresponding symmetry is absent in POE. Correlation with the freely jointed chain is investigated for the components of the tensors of fourth rank formed from the reduced vector \documentclass{article}\pagestyle{empty}\begin{document} $\tilde \rho = \left\langle {\rho \rho ^{\rm T} } \right\rangle ^{ - 1/2} \rho $\end{document}. Use of the equivalent chain model for this purpose is validated for POE but not for POM, even at n = 2000 bonds. At the limit 1/n = 0, the parameter m, representing the number of bonds of the real chain equivalent to one of the model, is estimated to be ca. 31 for POM. For POE a value of m = 10.3 ± 1.3 holds for n > 20 for all components. Results are compared with those calculated previously for polymethylene, poly(dimethylsiloxane) and polypeptides. The fact that values of m derived by analysis of moments are larger than those obtained in the usual manner by fitting the model chain to 〈r²〉₀ and r_max for the real chain demonstrates the inadequacy of artificial models for the representation of the real chain.