Infrared reflection-absorption spectroscopy of thin film structures

Infrared reflection-absorption spectroscopy has been used extensively in the study of adsorbates and thin films on metal surfaces, but little work has been performed on semiconductor and metal oxide surfaces due to the lack of sensitivity of the technique on these surfaces;In this work, IRRAS has been used to investigate the optical properties of thin film structures consisting of an optically thin layer of the nonmetallic component on an optically thick reflecting metal film. The sensitivity of the technique has been investigated by the use of thin polymer films of various thickness spun on thin film structures and compared with the transmission infrared spectra of similar films. The technique showed remarkable sensitivity to the thin films, several orders of magnitude more sensitivity than the corresponding transmission spectra. The technique was applied to the deposition of thin palladium films on silicon and copper surfaces by the decomposition of palladium acetate. Thin films of the acetate reacted much differently under oxidizing and reducing atmospheres and on different substrates, suggesting that substrate interactions play an important role in the decomposition process;Investigations were performed in order to determine the applicability of the technique to the study of thin layers and adsorbed molecules on metal oxide catalyst materials. It was determined that the technique exhibits sufficient sensitivity for the study of reaction and adsorption processes on metal oxide surfaces while avoiding the limitations of low surface area and low infrared transmittance. In addition, structural and compositional changes in the thin films were easily observed. The reactions of thin molybdenum trioxide films were studied in order to investigate the sensitivity of the technique to thin catalyst films. Both structural and compositional changes in thin oxide films were easily observable as a function of the atmosphere and reacting molecules above the film

Fermi Large Area Telescope Constraints on the Gamma-ray Opacity of the Universe

The Extragalactic Background Light (EBL) includes photons with wavelengths from ultraviolet to infrared, which are effective at attenuating gamma rays with energy above ~10 GeV during propagation from sources at cosmological distances. This results in a redshift- and energy-dependent attenuation of the gamma-ray flux of extragalactic sources such as blazars and Gamma-Ray Bursts (GRBs). The Large Area Telescope onboard Fermi detects a sample of gamma-ray blazars with redshift up to z~3, and GRBs with redshift up to z~4.3. Using photons above 10 GeV collected by Fermi over more than one year of observations for these sources, we investigate the effect of gamma-ray flux attenuation by the EBL. We place upper limits on the gamma-ray opacity of the Universe at various energies and redshifts, and compare this with predictions from well-known EBL models. We find that an EBL intensity in the optical-ultraviolet wavelengths as great as predicted by the "baseline" model of Stecker et al. (2006) can be ruled out with high confidence.Comment: 42 pages, 12 figures, accepted version (24 Aug.2010) for publication in ApJ; Contact authors: A. Bouvier, A. Chen, S. Raino, S. Razzaque, A. Reimer, L.C. Reye

All-sky Medium Energy Gamma-ray Observatory: Exploring the Extreme Multimessenger Universe

The All-sky Medium Energy Gamma-ray Observatory (AMEGO) is a probe class mission concept that will provide essential contributions to multimessenger astrophysics in the late 2020s and beyond. AMEGO combines high sensitivity in the 200 keV to 10 GeV energy range with a wide field of view, good spectral resolution, and polarization sensitivity. Therefore, AMEGO is key in the study of multimessenger astrophysical objects that have unique signatures in the gamma-ray regime, such as neutron star mergers, supernovae, and flaring active galactic nuclei. The order-of-magnitude improvement compared to previous MeV missions also enables discoveries of a wide range of phenomena whose energy output peaks in the relatively unexplored medium-energy gamma-ray band

Is Evil Good for Religion? The Link between Supernatural Evil and Religious Commitment

“The devil made me do it” is a familiar cliché often used to justify a bad decision. However, are beliefs in a devil or other evil supernatural beings actually beneficial for religion? Building upon Stark and Bainbridge (1987) and elements of the supernatural punishment hypothesis, this study proposes and tests the hypothesis that a positive relationship exists between the belief in supernatural evil and religious commitment. Data from 2007 Baylor Religion Survey reveal a strong positive correlation between the belief in supernatural evil and four measures of religious commitment: church attendance, religious perception, tithing, and faith sharing. This study not only contributes to a long discussion of religious commitment, but it also has implications for the growing literature on god images and the supernatural punishment hypothesis