Photoelectron spectroscopy of S1 toluene: II. Intramolecular dynamics of selected vibrational levels in S1 toluene studied by nanosecond and picosecond time-resolved photoelectron spectroscopies

We present results which suggest that the photophysics of S(1) toluene is significantly more complicated than that of the related molecules p-fluorotoluene or p-difluorobenzene. We have measured a range of photoelectron spectra for a number of S(1) internal energies, on different time scales and at different temperatures, in an attempt to unravel the competing processes, but the final conclusion remains outstanding.     

Harmonic detection with tunable diode lasers —two-tone modulation

The minimum absorption detectable by a tunable diode laser spectrometer utilising harmonic techniques is often limited by interference fringes generated by scattered light. The sensitivity of the spectrometer to absorption can be increased by applying a jitter modulation. In this paper, the theory of harmonic response for single- and two-tone modulation over optical fringes and Lorentzian absorption lines is developed and compared to experimental measurements. A simple analytic expression for the two-tone harmonic line shape is derived. This expression provides a physical understanding of the effects of the second modulation, and a means to unravel the effects of the second modulation on the linewidth and line shape. For a specific choice of the jitter frequency and phase, it is possible to simultaneously minimise the fringe signal and increase the harmonic absorption signal. The results of this investigation are applicable to trace gas detection using tunable diode lasers, and to other areas of spectroscopy and magnetic resonance where harmonic techniques are used.This work was supported by the Natural Sciences and Engineering Research Council of Canada, and the Ontario Ministry of the Environment     

Uniform Asymptotic Approximations to the Solutions of the Orr-Sommerfeld Equation Part 2. The General Theory

This paper deals with the derivation of “first approximations” to the solutions of the Orr-Sommerfeld equation which are uniformly valid in a full neighborhood of the critical point. To this order the theory is remarkably simple. The essential elements in the theory are all well known from the older heuristic theories but its general structure is substantially different. The uniform approximations are also vastly simpler than the composite approximations obtained recently by the method of matched asymptotic expansions.     

A moiré fringe alignment aid

The task of accurately superimposing two photographic transparencies is frequently encountered in some areas of optical metrology. By recording a suitable line structure, along with the image, on each photograph, moiré fringes formed when two of the structures are superimposed can be used to give an accurate indication of the alignment of the transparencies.     

Bypasses in asymmetric digraphs

A digraph G is said to be asymmetric if uv ∈ G implies vu ? G. If uv ∈ G and P is a path of length k from u to v, then P is called a k-bypass from u to v. In this paper we investigate asymmetric digraphs in which each line has a 2-bypass. Results are obtained on the existence of such digraphs, the relationship between 2-bypasses and longer bypasses, and the question of how prevalent such digraphs are.     

An electron microscope study of tin dioxide and antimony-doped tin dioxide

Crystals of tin dioxide, SnO₂, have been grown pure or doped with a few percent of antimony using vapor growth methods in order to investigate the microstructures of reduced and oxidized SnO₂. They were examined by X-ray diffraction and by optical and electron microscopy. SnO₂ crystals were found to contain few faults, but the antimony-doped crystals were extensively twinned in some regions. Reduction of SnO₂ crystals to yield CS phases was unsuccessful. These results are discussed in terms of the known crystal chemistry of the oxides involved.     

Linearization of a class of n coupled Bernoulli equations

Analytic linearization maps are found for autonomous systems of n coupled Bernoulli equations of a certain class. The class of equations is determined by the requirement that the nonlinear system linearize to its linear part. These equations have applications as models for interacting biological systems.