Some observations on left absolutely flat monoids

Communicated by J.M. Howie     

Measurement and analysis of the ν2 and ν4 infrared bands of 13CD4

A Fourier transform infrared spectrum of 91% ¹³CD₄ has been recorded between 885 and 1193 cm^?1 with a resolution of 0.04 cm^?1. The frequencies of 600 lines were measured with an accuracy of ±0.003 cm^?1. Of these, approximately 368 are assigned as allowed transitions in ν₄, 95 are forbidden ν₄ transitions, and 137 belong to ν₂; maximum upper state J values are 20 for ν₄ and 19 for ν₂. The ground state tensor constants D_t, H_4t, and H_6t were obtained by fitting them to four rotational transitions observed by Kreiner and Opferkuch in the infrared-microwave double-resonance spectrum. An interacting-band analysis of the $\text{ν}{}_2\text{ν}{}_4$ diad then yields 22 spectroscopic constants for these Coriolis-coupled fundamentals and fits the experimental frequencies with an rms deviation of 0.0055 cm^?1 for 432 unblended lines that were assigned unit weight. A ν₄P⁺(12) transition at 943.3812 cm^?1, nearly coincident with the 10P(22) emission of the ¹²C¹⁶O₂ laser, has been investigated by heterodyne spectroscopy and its detuning (?64 MHz) and absorption coefficient have been determined. Such coincidences may lead to the development of laser analytical techniques for ¹³CD₄, which is a useful nonradioactive atmospheric tracer. ¹³CD₄ transitions that are within 300 MHz of isotopic CO₂ laser lines are tabulated for this purpose and for use in double-resonance experiments.     

A new single-center perturbation theory for the treatment of simple hydrides

The perturbation expansion of Hartree-Fock potential energy surfaces of simple hydrides in a single-center scale 1/Z-expansion is carried out using diagrammatic methods. Diagrams having the topological structure of third-order diagrams are summed to all orders using an integral equation technique. The resulting one-electron wavefunction is used to generate a resummed perturbation series correct through fourth order.     

New indexing methods improve the computer retrieval of information on chemical separations

Finding a suitable method for a chemical separation in the literature is difficult. A new keywording/indexing method makes retrieval of information on a specific separation easy.     

Determination of selenium in individual food items using the short-lived nuclide77mSe

The selenium content of a variety of food items representing a normal hospital diet has been determined by cyclic instrumental neutron activation analysis (CINAA) through the 162-keV gamma-ray of the^77mSe nuclide. The CINAA method is very simple and rapid. It involves irradiation of a sample for 20 s, decay for 20 s, and counting for 20 s. The precision of the method has been significantly improved by recycling the samples up to 4 times. The accuracy has been evaluated by analyzing a number of certified reference materials of varied selenium levels.     

X-ray photoelectron spectroscopy of nitroanilines and their derivatives

N 1s core-electron spectra have been studied for nitroanilines and related compounds. The spectral data are qualitatively interpreted by means of the molecules-in-molecule method, which describes the interaction between the aromatic amine part (donor moiety) and the nitro group (acceptor moiety) in terms of a composite system consisting of a donor and an acceptor. It was found that the nitro-N 1s spectra and the separation between the nitro-N 1s and the amino-N 1s ionization energies depend upon the magnitude of the intramolecular charge-transfer interaction in the ground state. A similarity between the relaxation effect in the nitro-N 1s or nitro-O 1s core-hole ion and a nitration reaction of the donor moiety is demonstrated.     

High-resolution inverse Raman spectroscopy of the ν1 band of 28SiH4

A near-Doppler-limited isotropic Raman spectrum of the symmetric stretching fundamental ν₁ of ²⁸SiH₄ has been recorded between 2182.8 and 2187.0 cm^?1 using high-sensitivity “quasi-cw” inverse Raman spectroscopy. The band exhibits compact, nonoverlapping J manifolds, which were measured from Q(0) through Q(13), plus a portion of Q(14). Since ν₁ is in resonance with the nearby infrared-active stretch ν₃, these two bands were analyzed simultaneously using the infrared frequencies of ν₃ reported by Cabana, Gray, Robiette, and Pierre. The results confirm their analysis, in which several perturbation-allowed ν₁ transitions were identified in the infrared, but the molecular constants for the v₁ = 1 state are much better determined with the inclusion of the Raman data. At higher J, ν₁ exhibits significant intensity perturbations due to a breakdown of the selection rule ΔN = 0; these have been quantitatively accounted for.     

Assignment of the doublet states arising from ionization of chlorine lone-pairs in molecules possessing C2υ symmetry

The He(I) photoelectron spectra of Cl₂CCH₂, Cl₂CCF₂, Cl₂CF₂ and Cl₂CBr₂ have been recorded. Detailed assignments of the