Cis-trans isomerization of iodine-doped polyacetylene

A quantitative analysis of the cis—trans isomerization of the lightly doped polyacetylene with iodine at room temperature is reported. The cis—trans ratio was determined on the basis of the infrared absorption measurement. The result clearly demonstrates the promotion of the isomerization with increase in the dopant concentration. The degree of the amount of the isomerization, however, is rather small compared with the previous study based on the nuclear magnetic resonance measurement.     

The photodisintegration of 24Mg

The giant dipole resonance (GDR) of ²⁴Mg was studied by measuring two different types of decay spectra: (a) prompt de-excitation γ-rays emitted following photodisintegration, and (b) those of charged photoparticles. Energy-integrated (γ, n) and (γ, p) cross sections to specific residual states and also partial (γ, p) and (γ, α) cross sections are presented. The observed decay properties are discussed with reference to the 1p1h model, and the isospin purity of the GDR is assessed. Detailed comparison with theoretical models, however, indicates that the existing calculations fail to describe correctly both the deduced 1p1h composition and structure of the GDR.     

Einflu? des pH-Wertes und der Salzkonzentration auf die Helix-Kn?uel-Umwandlung von Poly A nach einer modifizierten DSC-Methode

Ohne Zusammenfassung     

Dielectric loss of polyethylene at very low temperatures in the frequency range from 1 kHz to 100 MHz

The dielectric loss of high-density polyethylene was measured from 1 kHz to 100 MHz with the improved calorimetric method at liquid-helium temperature for samples with different oxidation times t. Two loss peaks, centered at ca. 4 kHz and at 1 MHz, both increase in height with increasing t. On the bases of these results along with previously reported ones, the low-frequency and high-frequency losses are ascribed to the tunneling of protons of OH groups in crystalline and amorphous regions, respectively.     

Deuteron breakup with 3He at 89.4 and 118.9 MeV

Quasifree processes were studied by measuring coincident energy spectra for the ²H(³He, ³Hep)n, ²H(³He, tp)p and ²H(³He, dd)p reactions at 89.4 and 118.9MeV. The spectral shape was reproduced with two types of spectator model, that is, a three-body model (TBM) and a four-body model (FBM). The latter contains the effects of projectile breakup processes. Angular correlations of peak cross sections were explained by calculations in the FBM in contrast with those in the TBM. The absolute cross sections were not explained by either model.     

Adiabatic compressibility of critical binary mixtures of nitroethane/isooctane and nitroethane/3-methylpentane

The adiabatic compressibility β_S of nitroethane/isooctane is measured from 18 to 900 Hz at reduced temperatures ? ranging from 5 × 10^-5 to 5 × 10^-2. The zero-frequency compressibility extrapolated from the data is related with the specific heat at constant pressure c_p through the theory of Ferrell and Bhattacharjee (FB). The coupling constant g is evaluated from this relation as 0.38, which agrees with that from the thermodynamic definition of g. β_S at 900 Hz is observed for nitroethane/3-methylpentane at ? 5 × 10^-5-6 × 10^-2. A linear plot of the critical part of β_S against 1n? gives g = 0.34, which agrees with g from the thermodynamic definition and also with that from ultrasonic absorption. Numerical values of the critical and background components of β_S, the isothermal compressibility β_T, c_p, the specific heat at constant volume c_v, and the thermal expansion coefficient α_p are calculated for the two mixtures. The expression of β_S from Anisimov's theory is found to be consistent with that from the FB theory.     

A new method for calculation of the magnetic properties in one- and two-dimensional spin systems with anisotropic Heisenberg exchange

A new approximation method is proposed for the calculation of the magnetic susceptibility of one-dimensional assembly of spins and the critical temperature of two-dimensional one both with the anisotropic Heisenberg exchange. In a linear chain system, every spins are grouped into pairs of adjacent spins (pair-approximation) or clusters of adjacent three spins ((q+1)-approximation), and the partition function of the total spin system is approximated as a sum of products of the partitions functions for the pairs or the clusters. Then the partition function of the anisotropic Heisenberg spin system is shown to reduce into a form of the Ising spin system with modified coupling constants. The exact result for the Ising chain system enables us to obtain an analytical expression for the magnetic susceptibility of anisotropic Heisenberg chain system. The same approximations are also applied to two-dimensional lattices, and the critical temperatures of the square, triangular, and honeycomb lattices with anisotropic Heisenberg exchange are calculated as a function of anisotropy parameter. The results are compared with those of the existing theories and shown to be quite excellent.     

Isotopically selective CVD of silicon by IRMPD of Si2F6

The IRMPD of Si₂F₆ by a CO₂ TEA laser was applied to isotopically selective CVD of silicon. A white film, probably consisting of polymers of SiF₂, was deposited on a metal foil during the irradiation of natural Si₂F₆ with the laser radiation at 951.19 cm^–1 and about 1.5 J cm^–2. Upon heating, the film became dark brown, evolving SiF₄. The³⁰Si content was found to be as high as about 20%.