Two novel cassane diterpenoids from Acacia jacquemontii

The structure of two new diterpenoids (1 and 3), both of which contain the unique feature of a 7-membered hemiacetal ring B, have been established from chemical and spectroscopic (especially NMR) evidence. Single crystal X-ray crystallographic analysis of 1 has confirmed the structure and allowed the relative stereochemistry to be determined.     

Effect of Flat Top Electron Distribution on the Turbulent Heating of a Plasma

Expressions for anomalous resistivity and energy transfer collision frequency in the presence of ion-acoustic instability have been derived. It is found that the rapid electron heating may be attributed to the flattening of the top of the electron distribution function to a high degree. Results are valid under the situation when krr_c « 1 where τ_c is the correlation time for turbulence.     

Effective interactions and the 1f72 sub-shell closure in the 2p-1f shell

It is estimated that the ground state of ⁵⁶Ni as given by the Kuo-Brown effective interaction modified to satisfy the restrictions imposed by the BE2 systematics contains about 13 particles in the $\text{1f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ shell.     

A modified Del Re method

A modified computational Del Re procedure is exposed. The method allows the user to spare a large amount of time and storage, together with the possible study of large molecules up to two hundred atoms or more.Sponsored in part by the Instituto de Biología Fundamental. Universidad Autónoma de Barcelona.     

TheB 2Σ-X 2Σ system of the CaF molecule

The spectrum of theB ²Σ-X ²Σ system of the CaF molecule has been photographed in the second order of a 10.6 m concave grating spectrograph with 0.33 Å/mm dispersion. The rotational structure of the (0, 0) and (1, 0) bands has been analysed and the precise molecular constants have been obtained. Using the constants so determined the band origins of a large number of bands with 0 <v′,v″ < 10 have been calculated and used to obtain the accurate vibrational constants forB andX states and these are presented.     

Positron annihilation in solid krypton and xenon

A computation of the life time of positrons as well as the angular distribution of the resulting gamma pair for polycrystalline krypton and xenon has been made. The calculations are based on the technique employed by Salvadori and Carbotte for the case of solid argon. The field seen by the positrons is constructed from the charge densities derived from Herman-Skillman wave functions. The positron wave functions are obtained using the Wigner-Seitz approximation. For electrons Herman-Skillman wave functions have been used. The computed distributions, when the effects of correlation are ignored, are wider than the experimental ones. The calculated values for the mean lives of positrons for krypton and xenon are 2.2×10⁻⁹ sec and 2.7×10⁻⁹ sec, respectively, and that for xenon is, as usual, longer than the measured value of 0.43×10⁻⁹ sec. Effects of electronpositron correlations on the angular distribution and the life time have been calculated for the case of krypton. When these corrections are taken into account, the life time of positrons in krypton is reduced by a factor of about eight and the angular distribution shows a slight narrowing. Paper A24 presented at 3rd Internat'l Conf. Positron Annihilation, Otaniemi, Finland (August 1973).     

Advances in the use of computer techniques in flame photometry

The range and complexity of the application of computer techniques in flame photometry methods has been extended. Improvements in output formatting are detailed and typical automated analyses are presented. Examples are discussed from both mathematical and analytical points of view. The potential of graphic display consoles is explained in detail.     

Hartree-Fock-Bogolubov projected spectra for Cr and Fe isotopes and the effective interactions in the 2p-1f shell

The intrinsic states of Cr and Fe isotopes are obtained by carrying out deformed Hartree-Fock-Bogolubov calculations employing the Kuo-Brown effective interaction for the 2p-1f shell modified slightly to satisfy the restrictions imposed on it by the B (E2) (0→2) systematics in the shell. The angular momentum projected spectra resulting from the modified interaction are in good agreement with the experimental results.