The electron’s self photon

Equations of motion (EOM’s) are presented for the electron and photon. The electron EOM is the same as Dirac’s equation with mass interpreted to be totally electromagnetic in nature. The photon EOM is considered here to be the EOM for the electron’s self photon. The electron EOM and photon EOM together are presented as a single theory of the electron which is distinct from QED, in which separate matter and light theories are used for the electron and photon respectively.A temporarily bound state is found for the point proton-electron-self-photon three-body combination which possibly represents a neutronic state. In support of this surmise the theory is used to calculate the neutronic state-proton mass difference, the lifetime of the neutronic state against electron emission, and the neutronic state’s magnetic moment. This interpretation of the neutronic state suggests that the self photon and the neutrino share the same EOM and are possibly the same particle.     

A DFG-based cavity ring-down spectrometer for trace gas sensing in the mid-infrared

Continuing studies into an all-diode laser-based 3.3 μm difference frequency generation cavity ring-down spectroscopy system are presented. Light from a 1,560 nm diode laser, amplified by an erbium-doped fibre amplifier, was mixed with 1,064 nm diode laser radiation in a bulk periodically poled lithium niobate crystal to generate 16 μW of mid-IR light at 3,346 nm with a conversion efficiency of $0.05\,\%\,{\text{W}}^{-1}\,{\text{cm}}^{-1}$ . This radiation was coupled into a 77 cm long linear cavity with average mirror reflectivities of 0.9996, and a measured baseline ring-down time of $6.07\pm 0.03\,\upmu{\rm s}$ . The potential of such a spectrometer was illustrated by investigating the $P(3)$ transition in the fundamental $\nu_{3}(F_{2})$ band of ${\text{CH}}_4$ both in a 7.5 ppmv calibrated mixture of ${\text{CH}}_4$ in air and in breath samples from methane and non-methane producers under conditions where the minimum detectable absorption coefficient ( $\alpha_{\rm min}$ ) was $2.8 \times 10^{-8}\,{\rm cm}^{-1}$ over 6 s using a ring-down time acquisition rate of 20 Hz. Allan variance measurements indicated an optimum $\alpha_{\rm min}$ of $2.9\times 10^{-9}\,{\rm cm}^{-1}$ over 44 s.     

Zeeman splitting in ballistic hole quantum wires

We have studied the Zeeman splitting in ballistic hole quantum wires formed in a (311)A quantum well by surface gate confinement. Transport measurements clearly show lifting of the spin degeneracy and crossings of the subbands when an in-plane magnetic field B is applied parallel to the wire. When B is oriented perpendicular to the wire, no spin splitting is discernible up to B = 8.8 T. The observed large Zeeman splitting anisotropy in our hole quantum wires demonstrates the importance of quantum confinement for spin splitting in nanostructures with strong spin-orbit coupling.     

Thermodynamic density of states of two-dimensional GaAs systems near the apparent metal-insulator transition

We perform combined resistivity and compressibility studies of two-dimensional hole and electron systems which show the apparent metal-insulator transition--a crossover in the sign of deltaR/deltaT with changing density. No thermodynamic anomalies have been detected in the crossover region. Instead, despite a tenfold difference in r(s), the compressibility of both electrons and holes is well described by the theory of nonlinear screening of the random potential. We show that the resistivity exhibits a scaling behavior near the percolation threshold found from analysis of the compressibility. Notably, the percolation transition occurs at a much lower density than the crossover.     

The growth of GaAs and InAs dots on etched mesas: The effect of substrate temperature on mesa profile and surface morphology on dot distribution

The molecular beam epitaxy (MBE) growth of GaAs and InAs quantum dots on etched mesas has been studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The [0 1 1]-oriented mesas are etched into (1 0 0) GaAs substrates, exposing (5 3 3)B sidewall facets. At a substrate temperature of 610 °C a top (1 0 0) plane is seen to evolve on a ridge mesa structure. Alternatively, if the overgrowth is carried out at 630 °C no such facet is seen, and the top ridge remains unchanged during GaAs growth. By controlling the mesa shape, either ordered lines of dots can be grown or the dot density can be varied from <5×10⁸ cm⁻² to >1×10¹¹ cm⁻² on the same substrate in pre-defined regions. The dot distribution observed on the mesa sidewalls and top is discussed in terms of net migration of adatoms from different facets, underlying step density, step height and surface curvature of the mesa top.     

Diffusion of dextran within poly(methacrylic acid) hydrogels

We describe an investigation of fluorescence correlation spectroscopy into the diffusion of fluorescein‐tagged dextran (FDEX) in a poly(methacrylic acid) (PMAA) hydrogel. The temperature dependence of FDEX diffusion is shown to follow Zimm behavior in pure water, and the decrease in the diffusion coefficient when in the PMAA hydrogel has been modeled. The addition of acid and alkali (HCl and NaOH, respectively) not only control the swelling and collapse of the hydrogel but also reveal a strong pH dependence of the dextran diffusion coefficient, which shows a (nonmonatonic) increase with pH. The addition of NaCl and CaCl₂ salts similarly showed evidence of network swelling, most notably at low salt concentration, but also that the diffusion coefficient within the gel at these low concentrations is larger than that in the equivalent solution without the hydrogel, indicating that the combination of hydrogel and salt works to increase the diffusion coefficient above that in pure water. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

nσ* and πσ* excited states in aryl halide photochemistry: a comprehensive study of the UV photodissociation dynamics of iodobenzene

A recent review (Ashfold et al., Phys. Chem. Chem. Phys., 2010, 12, 1218) highlighted the important role of dissociative excited states formed by electron promotion to σ* orbitals in establishing the photochemistry of many molecular hydrides. Here we extend such considerations to molecular halides, with a particular focus on iodobenzene. Two experimental techniques (velocity mapped ion imaging (VMI) and time resolved infrared (IR) diode laser absorption) and electronic structure calculations have been employed in a comprehensive study of the near ultraviolet (UV) photodissociation of gas phase iodobenzene molecules. The VMI studies yield the speeds and angular distributions of the I((2)P(3/2)) and I*((2)P(1/2)) photofragments formed by photolysis in the wavelength range 330 ≥λ≥ 206 nm. Four distinct dissociation channels are observed for the I((2)P(3/2)) atom products, and a further three channels for the I*((2)P(1/2)) fragments. The phenyl (Ph) radical partners formed via one particular I* product channel following excitation at wavelengths 305 ≥λ≥ 250 nm are distributed over a sufficiently select sub-set of vibrational (v) states that the images allow resolution of specific I* + Ph(v) channels, identification of the active product mode (ν(10), an in-plane ring breathing mode), and a refined determination of D(0)(Ph-I) = 23,390 ± 50 cm(-1). The time-resolved IR absorption studies allow determination of the spin-orbit branching ratio in the iodine atom products formed at λ = 248 nm (?(I*) = [I*]/([I] + [I*]) = 0.28 ± 0.04) and at 266 nm (?(I*) = 0.32 ± 0.05). The complementary high-level, spin-orbit resolved ab initio calculations of sections (along the C-I bond coordinate) through the ground and first 19 excited state potential energy surfaces (PESs) reveal numerous excited states in the energy range of current interest. Except at the very shortest wavelength, however, all of the observed I and I* products display limiting or near limiting parallel recoil anisotropy. This encourages discussion of the fragmentation dynamics in terms of excitation to states of A(1) total symmetry and dissociation on the 2A(1) and 4A(1) (σ* ← n/π) PESs to yield, respectively, I and I* products, or via non-adiabatic coupling to other σ* ← n/π PESs that correlate to these respective limits. Similarities (and differences) with the available UV photochemical data for the other aryl halides, and with the simpler (and more thoroughly studied) iodides HI and CH(3)I, are summarised.     

Postcolumn derivatization of amino acids using reaction flow chromatography columns with fluorescence detection: A fast new approach to selective derivatization techniques

Reaction flow (RF) chromatography with fluorescamine reagent and fluorescence detection (FLD) was used for the analysis of amino acids. The performance of RF chromatography was tested against several optimized conventional postcolumn derivatization (PCD) methods. RF columns achieved greater sensitivity compared to conventional PCD methods, without the need for reaction loops, which resulted in more efficient separations. The RF-PCD method also achieved limits of detection (LOD) from the low picomole to subnanomole range. The calibration data of the RF-PCD technique yielded R²?≥?0.99 and % relative standard deviation in peak areas ranging from 0.34% to 5%. Through reaction flow chromatography, multiplexed detection was also achieved allowing the monitoring and analysis of derivatized and nonderivatized flow streams simultaneously.     

Preparation of Cellulose Acetate Supported Zero-Valent Iron Nanoparticles for the Dechlorination of Trichloroethylene in Water

Chlorinated hydrocarbons are an immense concern for human health and the environment because they␣are highly toxic and are present in many contaminated sites. Zero-valent iron has been shown to be very effective for the dechlorination of chlorinated olefins and paraffins. This behavior is enhanced when the particle size is in the nanometer range. The activity of these nanoparticles is very high, and thus supporting the particles is important to preserve their chemical nature by inhibiting oxidation until they can be contacted with the chlorinated stream. In this paper, we present the preparation of membrane (cellulose acetate) supported zero-valent iron nanoparticles. The highly active nanoparticles were synthesized in a water-oil micro-emulsion, mixed with cellulose acetate-acetone solution, and then formed into a porous membrane by phase inversion. The unsupported iron particles and membrane supported iron particles were characterized using transmission electron microscopy. Batch experiments were conducted to characterize the activity of the supported zero-valent iron nanoparticles to dechlorinate trichloroethylene in water, as well as to investigate synergistic effects of the polymer support matrix.