Spectral Signatures of Photon-Particle Oscillations from Celestial Objects

We give detailed predictions for the spectral signatures arising from photon-particle oscillations in astrophysical objects. The calculations include quantum electrodynamic effects as well as those due to active relativistic plasma. We show that, by studying the spectra of compact sources, it may be possible to directly detect (pseudo-)scalar particles, such as the axion, with much greater sensitivity, by roughly three orders of magnitude, than is currently achievable by other methods. In particular, if such particles exist with masses m_a<0.01[eV] and coupling constant to the electromagnetic field, g>1e-13[1/GeV], then their oscillation signatures are likely to be lurking in the spectra of magnetars, pulsars, and quasars.Comment: 29 pages (reduced resolution for figs. 3, 4b, 7

Influence of Silver Incorporation on the Structural and Electrical Properties of Diamond-Like Carbon Thin Films

A simple approach is proposed for obtaining low threshold field electron emission from large area diamond-like carbon (DLC) thin films by sandwiching either Ag dots or a thin Ag layer between DLC and nitrogen-containing DLC films. The introduction of silver and nitrogen is found to reduce the threshold field for emission to under 6 V/μm representing a near 46% reduction when compared with unmodified films. The reduction in the threshold field is correlated with the morphology, microstructure, interface, and bonding environment of the films. We find modifications to the structure of the DLC films through promotion of metal-induced sp bonding and the introduction of surface asperities, which significantly reduce the value of the threshold field. This can lead to the next-generation, large-area simple and inexpensive field emission devices. © 2013 American Chemical Society

NONEQUILIBRIUM IONIZATION IN MAGNETOHYDRODYNAMIC GENERATORS

The steady state ionization of a gas in which the electrons are hot and the atoms cool is investigated. The rate equations governing ionization, excitation, recombination, and de-excitation are solved for a model system using rate coefficients appropriate to the Cs atom. Included are all processes involving free electrons as well as spontaneous emission and resonance trapping of radiation. No incoming radiation is assumed, and the system is assumed large compared with a collisional mean free path but optically thin except for resonance radiation. The fractional ionization is computed for a range of electron temperatures and Cs densities of interest in MHD studies. It is found that there are reasonable conditions of temperature and density under which the ionization is close to that which would prevail if the system were in equilibrium at the electron temperature. At lower temperatures or densities, the ionization decreases but is still much greater than that appropriate to the gas temperature. (auth