In situ X-ray scattering studies of lyotropic liquid crystalline PBO and PBZT monofilament drawing

The results of a series of novel synchrontron-based in situ x-ray scattering experiments of monofilament fiber drawing from lyotropic solutions of poly(cis-benzoxazole) (PBO) and poly(trans-benzothiazole) (PBZT) are reported. The purpose of the study is to determine orientation and microstructure development in the draw zone as a function of shear rate in the capillary die, and spin draw ratio (SDR). The transition of the extrudate from opaque to the transparent is complete at about a SDR = 3 and f of 0.9. The filament orientation parameter (f) was found to depend strongly on spin draw ratio, but not shear rate. The orientation was found to increase down the extrudate toward completion of the draw down as one proceeds further from the die face up to an extrudate length of 3.8 cm. Coherence lengths on the order of 19 nm (axial), and 4.5 nm (lateral) have been observed. These “microdomain” sizes are consistent with the “crystallite” sizes typically observed in coagulated fiber. The occurrence of these microdomains in the draw zone as a precursor to the microfibrillar structure is believed to be the origin of low filament compressive strength. © 1994 John Wiley & Sons, Inc.     

A detailed consideration of resonance radiation trapping in the argon inductively coupled plasma

The extent and duration of trapping of argon resonance radiation (106.7 and 104.8 nm) in the ICP was calculated using a model incorporating line shape contributions from both Doppler and pressure broadening. The trap was found to be at the pressure-broadened limit, giving an escape factor of 7.9 × 10^?4 when excitation of the 4s states in the plasma annulus is assumed. Theoretical apparent radiative lifetimes τ_app for argon ³P₁ and ¹P₁ resonance states are calculated to be 8 and 1.9μs respectively. The quartet of 4s states, rapidly mixed by electron collisions, are presumed to share an overall apparent radiative lifetime τ_app = 1.6μs for the purpose of plasma modeling. Effects of this radiation trapping on the argon 4s atom density and on electron-ion recombination are discussed.     

The ν2, 2ν2, 3ν2, ν4, and ν2 + ν4 bands of 15NH3

The ir absorption of gaseous ¹⁵NH₃ between 510 and 3040 cm^?1 was recorded with a resolution of 0.06 cm^?1. The ν₂, 2ν₂, 3ν₂, ν₄, and ν₂ + ν₄ bands were measured and analyzed on the basis of the vibration-rotation Hamiltonian developed by V. ?pirko, J. M. R. Stone, and D. Papou?ek (J. Mol. Spectrosc.60, 159–178 (1976)). A set of effective molecular parameters for the ν₂ = 1, 2, 3 states was derived, which reproduced the transition frequencies within the accuracy of the experimental measurements. For ν₄ and ν₂ + ν₄ bands the standard deviation of the calculated spectrum is about four times larger than the measurements accuracy: a similar result was found for ν₄ in ¹⁴NH₃ by ?. Urban et al. (J. Mol. Spectrosc.79, 455–495 (1980)). This result suggests that the present treatment takes into account only the most significant part of the rovibration interaction in the doubly degenerate vibrational states of ammonia.     

Potential energy surface intersections for triatomic molecules

The different types of surface intersection which may occur in linear configurations of triatomic molecules are reviewed, particularly with regard to the way in which the degeneracy is split as the molecule bends. The Renner-Teller effect in states of symmetry Π, Δ, Φ, etc., and intersections between Σ and Π, Σ and Δ, and Π and Δ states are discussed. A general method of modelling such intersecting potential surfaces is proposed, as a development of the model previously used by Murrell and Carter and co-workers for single-valued surfaces. Some of the lower energy surfaces of H₂O, NH₂, O₃, C₃, and HNO are discussed as examples.     

Matrices of bisimple regular semigroups

A semigroup S is a matrix of subsemigroups S_iμ, i ε I, μ ε M if the S_iμ form a partition of S and S_iμS_jν≤S_iν for all i, j in I, μ, ν in M. If all the S_iμ are bisimple regular semigroups, then S is a bisimple regular semigroup. Properties of S are considered when the S_iμ are bisimple and regular; for example, if S is orthodox then each element of S has an inverse in every component S_iμ.     

Intensity perturbations due to ν3/ν4 Coriolis interaction in methane

Formulas are obtained for the intensity asymmetry (Herman-Wallis) factors in the ν₃ and ν₄ fundamentals of methane due to the ζ₃₄ Coriolis interaction. The results are also applicable to the ν₃ and ν₄ bands of SF₆.