We report new analyses of spectra of the 3.2–3.3 μ m absorption feature observed in the diffuse interstellar medium toward three Milky Way sources: 2MASS J 17470898 − 2829561 (2M1747) and the Quintuplet Cluster, both located in the Galactic center, and Cygnus OB2-12. The 3.2–3.3 μ m interval coincides with the CH-stretching region for compact polycyclic aromatic hydrocarbons (PAHs). We focus on the 2M1747 spectrum. Its published optical depth spectrum contains residual telluric transmission features, which arise from the 0.06 difference in mean airmasses between the observations of the source and its telluric standard star. We corrected the published spectrum by adding the airmass residual optical depth spectrum. The corrected spectrum is well fit by a superposition of four Gaussians. The absorption spectra of the other two sources were also fit by four Gaussians, with similar central wavelengths, widths, and relative peak opacities. We associate the three longer wavelength Gaussians covering the 3.23–3.31 μ m interval with compact PAHs in positive, neutral, and negative charge states. We identify the shortest-wavelength Gaussian, near 3.21 μ m, with irregularly shaped PAHs. Constraints imposed by spectral smoothness on the corrected 2M1747 spectrum, augmented by a PAH cluster formation model for post-asymptotic giant branch stars, suggests that >99% of the PAHs in the diffuse interstellar medium reside in small clusters. This study supports the PAH hypothesis, and it suggests that a family of primarily compact PAHs with a C _66 H _20 (circumvalene) parent is consistent with the observed mid-infrared and ultraviolet interstellar absorption spectrum.

Abstract Simultaneous spectroscopic observations of the carbon monoxide (CO) fundamental and first overtone emission are presented for the nova V496 Scuti. Total emission is comparable in the two features, indicating that optically thick conditions (optical depth τ ≈ 100) exist in the fundamental. Analysis of the first overtone suggests a temperature for the CO emitting region of ≥4000 K and a 13C to 12C ratio of 0.7 ± 0.1. Concurrent observations by Raj et al., found emission lines of C i and O i present at this time, indicating that carbon monoxide formation did not fully incorporate either of these two elements.

Abstract HD 44179 is a postasymptotic giant branch star with a biconical nebula known as the Red Rectangle. It shows the 3.3, 3.4, 6.2, 7.7, 8.6, and 11.3 μm infrared emission features (commonly known as the polycyclic aromatic hydrocarbon (PAH) emission bands and the Aromatic Infrared Bands). Previous observations of HD 44179 showed that the width of the 3.3 μm emission feature was narrower within 2″ of HD 44179 and wider further away from the star. This was interpreted as an indication that the 3.3 μm emission feature arises from two types of PAHs with spatially varying relative abundances. With new observations of HD 44179 taken with the NASA Infrared Telescope Facility we find that the width of the 3.3 μm emission feature profile is not narrower on HD 44179 and conclude that there is no evidence for two spatially varying components.

HD 44179 is a postasymptotic giant branch star with a biconical nebula known as the Red Rectangle. It shows the 3.3, 3.4, 6.2, 7.7, 8.6, and 11.3 mu m infrared emission features (commonly known as the polycyclic aromatic hydrocarbon (PAH) emission bands and the Aromatic Infrared Bands). Previous observations of HD 44179 showed that the width of the 3.3 mu m emission feature was narrower within 2 '' of HD 44179 and wider further away from the star. This was interpreted as an indication that the 3.3 mu m emission feature arises from two types of PAHs with spatially varying relative abundances. With new observations of HD 44179 taken with the NASA Infrared Telescope Facility we find that the width of the 3.3 mu m emission feature profile is not narrower on HD 44179 and conclude that there is no evidence for two spatially varying components.

We examine the self-consistency of laboratory and observational data for potential carriers of the 3.3 mu m infrared emission feature (IEF), a member of the ubiquitous family of strong interstellar IEFs at 3.3, 3.4, 6.2, 7.7, 8.6, 11.2, and 12.7 mu m. Previous studies have shown that most Galactic sources (reflection nebulae, H ii regions, and planetary nebulae) show 3.3 mu m IEFs displaying similar central wavelengths, FWHM, and profiles. Our study is focused on the band profile designated as Class A, the most prevalent of four classes of observed band profiles. In contrast to the observations, laboratory spectra for gas phase polycyclic aromatic hydrocarbons (PAHs), the widely assumed carriers of the IEFs, display central wavelength shifts, widths, and profiles that vary with temperature and PAH size. We present an extrapolation of the laboratory band shifts and widths for smaller PAHs (<= 32 carbon atoms) to the larger PAHs (>50 carbon atoms) that are thought to be the IEF carriers. The extrapolation leads to tight constraints on the sizes of the putative PAH carriers. Reconciling the observations with the implications of the laboratory spectra pose a significant challenge to the PAH and other IEF carrier hypotheses.

We model anomalous microwave emission (AME) spectral profiles from 14 diverse galactic and extragalactic sources. The spectral profile model is an analytic representation of a quantum mechanical model for symmetric top rotational emission. The observed spectral shapes are well fit by superposing two model profiles originating from two distinct carrier families. Each family is composed of numerous, comparably abundant isomers of a parent carrier. The isomers have similar rotational constants, thereby producing continuous, versus resolved line, spectra that are slightly broader than the parent profiles. Ten observations are fit with comparable peak height and peak frequency ratios for the two carrier families, suggesting that AME arises from common carriers. One observation is fit using a single family, attributed to photodissociation of the less stable, smaller molecules for the missing family. Three observations are fit by combining two frequency-shifted model spectra, indicating multiple sources along their sight lines. The derived rotational constants for the two parent carriers are well determined because their rotational temperature is well characterized for the LDN 1622 dark cloud AME source. The rotational constants are consistent with the C36 and C60 fullerenes as the parent carriers. We use a Monte Carlo simulation of fullerene hydrogenation to understand the origins of source variability in the AME model fits. Other potential carriers, polycyclic aromatic hydrocarbons and very small grains, cannot be excluded; however, we find that fulleranes are also viable carriers because their aromatic cages are extremely stable to photodissociation, and their data-derived sizes suggest C36 and C60 parent fullerenes.

Thin films of the electrically conducting polymer, poly(3-hexylthiophene) (P3HT), were developed as sensors for hydrazine vapor at the part-per-billion level. The P3HT films were fabricated by a spin coating technique onto quartz substrates incorporating gold interdigitated electrodes, and were rendered conductive by doping with an NOPF6 solution. The sensors respond strongly and instantaneously to hydrazine concentrations as low as 1 part-per-billion with a measurement accuracy of ±20%. In addition, the sensors exhibited excellent environmental stability, long shelf life, and good interference rejection.

We explore the common-carrier hypothesis for the 6196 and 6614 Å diffuse interstellar bands (DIBs). The observed DIB spectra are sharpened using a spectral deconvolution algorithm. This reveals finer spectral features that provide tighter constraints on candidate carriers. We analyze a deconvolved λ6614 DIB spectrum and derive spectroscopic constants that are then used to model the λ6196 spectra. The common-carrier spectroscopic constants enable quantitative fits to the contrasting λ6196 and λ6614 spectra from two sightlines. Highlights of our analysis include (1) sharp cutoffs for the maximum values of the rotational quantum numbers, Jmax = Kmax, (2) the λ6614 DIB consisting of a doublet and a red-tail component arising from different carriers, (3) the λ6614 doublet and λ6196 DIBs sharing a common carrier, (4) the contrasting shapes of the λ6614 doublet and λ6196 DIBs arising from different vibration–rotation Coriolis coupling constants that originate from transitions from a common ground state to different upper electronic state degenerate vibrational levels, and (5) the different widths of the two DIBs arising from different effective rotational temperatures associated with principal rotational axes that are parallel and perpendicular to the highest-order symmetry axis. The analysis results suggest a puckered oblate symmetric top carrier with a dipole moment aligned with the highest-order symmetry axis. An example candidate carrier consistent with these specifications is corannulene (C20H10), or one of its symmetric ionic or dehydrogenated forms, whose rotational constants are comparable to those obtained from spectral modeling of the DIB profiles.

We describe a new algorithm, QUAC-IR (QUick Atmospheric Correction in the InfraRed), for automated, fast, atmospheric correction of LWIR (Long Wavelength InfraRed) hyperspectral imagery (HSI) and multi-spectral imagery (MSI) in the ~7-14 mm spectral region. QUAC-IR is an in-scene based algorithm, similar to the widely used ISAC (In- Scene Atmospheric Correction) algorithm. It improves upon the ISAC approach in several key ways, including providing absolute, versus relative, sensor-to-ground transmittances and radiances, as well as an estimate of the atmospheric downwelling sky radiance. The latter is important for retrieving emissivity from a reflective (i.e., non-blackbody) pixel. The key aspect of QUAC-IR is that it explicitly searches for blackbody pixels using an efficient approach involving a small number of spectral channels in which the atmospheric radiative transfer is dominated by the water continuum. This allows for fast and simplified Beer's Law (i.e., exponential) scaling of the path transmittance and radiance based on a compact library of pre-computed reference values. We apply QUAC-IR to well-calibrated data from the SEABASS1 and MAKO2 HSI sensors. The results are compared to those from a first-principles physics-based atmospheric code, FLAASH-IR.

Extremely thick haze caused by air pollution is observed in many satellite images of the earth, and in particular over eastern China. Standard image display software typically provides satisfactory visualization of the ground through automated or user-driven scaling to enhance contrast; however, it does not perform well with these highly polluted scenes, where the haze is spatially non-uniform. Furthermore, estimation of surface reflectance using standard atmospheric correction software is highly problematic under these conditions due to very low visible transmission of the haze coupled with lack of knowledge of its optical properties, which may not conform to the haze or aerosol models in the software. In this paper we show that a version of the empirical Quick Atmospheric Correction (QUAC) algorithm, adapted for spatially dependent scattering, produces visually satisfying imagery of the entire ground in multispectral satellite scenes containing thick haze, and that the output reflectance spectra appear to be realistic enough for performing basic surface classification. The QUAC algorithm is applicable to multispectral and hyperspectral imagery with any number of wavelength bands, including true color (RGB) imagery, and does not require radiometrically calibrated data.

We analyze the spectrum of the 11.2 μ m unidentified infrared band (UIR) from NGC 7027 and identify a small fullerene (C 24 ) as a plausible carrier. The blurring effects of lifetime and vibrational anharmonicity broadening obscure the narrower, intrinsic spectral profiles of the UIR band carriers. We use a spectral deconvolution algorithm to remove the blurring, in order to retrieve the intrinsic profile of the UIR band. The shape of the intrinsic profile—a sharp blue peak and an extended red tail—suggests that the UIR band originates from a molecular vibration–rotation band with a blue band head. The fractional area of the band-head feature indicates a spheroidal molecule, implying a nonpolar molecule and precluding rotational emission. Its rotational temperature should be well approximated by that measured for nonpolar molecular hydrogen, ∼825 K for NGC 7027. Using this temperature, and the inferred spherical symmetry, we perform a spectral fit to the intrinsic profile, which results in a rotational constant implying C 24 as the carrier. We show that the spectroscopic parameters derived for NGC 7027 are consistent with the 11.2 μ m UIR bands observed for other objects. We present density functional theory (DFT) calculations for the frequencies and infrared intensities of C 24 . The DFT results are used to predict a spectral energy distribution (SED) originating from absorption of a 5 eV photon, and characterized by an effective vibrational temperature of 930 K. The C 24 SED is consistent with the entire UIR spectrum and is the dominant contributor to the 11.2 and 12.7 μ m bands.

Developed in response to concerns that too few students were enrolling and succeeding in postsecondary education, early college high schools are small schools that blur the line between high school and college. This article presents results from a longitudinal experimental study comparing outcomes for students accepted to an early college through a lottery process with outcomes for students who were not accepted through the lottery and enrolled in high school elsewhere. Results show that treatment students attained significantly more college credits while in high school, and graduated from high school, enrolled in postsecondary education, and received postsecondary credentials at higher rates. Results for subgroups are included.

We argue that the observed spectroscopic and statistical properties of the diffuse interstellar band (DIB) carriers are those that are needed to produce the anomalous microwave emission (AME). We explore this idea using a carrier-impartial model for AME based on the observed DIB statistical properties. We show that an observed distribution of profile widths for narrow DIBs can be mapped into an AME spectrum. The mapping model is applied to width distributions observed for HD 204827 and HD 183143, selected because their spectroscopic and statistical properties bracket those for most other sight lines. The predicted AME spectra for these sight lines agree well with the range of spectral shapes, and peak frequencies, ∼23–31 GHz, typically observed for AME. We use the AME spectral profiles to derive a strong constraint between the average carrier size and its rotational temperature. The constraint is applied to a variety of postulated molecular carrier classes, including polycyclic aromatic hydrocarbons, fulleranes, hydrocarbon chains, and amorphous hydrocarbon clusters. The constraint favors small, cold carriers with average sizes of ∼8–15 carbon atoms, and average rotational temperatures of ∼3–10 K, depending on carrier type. We suggest new observations, analyses, and modeling efforts to help resolve the ambiguities with regard to carrier size and class, and to further clarify the DIB–AME relationship.

We present an analysis of the diverse spectral profiles observed for the lambda 6614 diffuse interstellar band (DIB). This includes the anomalous Herschel 36 profile, exhibiting a prominent, broad red tail, and the typically observed narrow profiles, exhibiting much narrower, but noticeable red tails. This study was motivated by the inability of previous rotational contour modeling work to account for the narrow and broad red tails. We show that the full profiles, for all the observations, can consistently be modeled as a superposition of two overlapping DIBs, with peaks at 6613.6 and 6614.2 angstrom. Each DIB is plausibly fit using a prolate, parallel band, symmetric top spectral contour model. For lambda 6613.6, there are small differences in the rotational constants, less than 1%, between the upper and lower transition states; whereas, for lambda 6614.2, the differences are much larger, similar to -5%. These results are consistent with lambda 6614.2 being the source of the narrow and broad red tails. The fit residuals are shown to be consistent with contributions from overlapping spectra, attributed to closely spaced vibrational sequences, originating from low frequency vibrations. We suggest that such sequences may be the source of the anomalous broadening needed to obtain good spectral fits to narrow DIB profiles. We discuss how lambda 6614.2 and the other Herschel 36 extended red tail DIBs help bridge the association gap between the narrow, absorption DIBs and the even broader and more redshifted emission features observed for the Red Rectangle. Finally, the broader implications of this study, in the context of identifying DIB molecular carriers, are discussed.

The quick atmospheric correction (QUAC) algorithm is a relatively fast and robust atmospheric compensation algorithm for hyperspectral image processing utilizing in scene information. An adjustment of some key parameters in QUAC is made leading to improved results for coastal scenes. In general the QUAC results compare well with two first principles radiative transfer (RT) model based algorithms. Some suggestions for future work are made including automating the setting of key QUAC parameters and accounting for the coastal zone aerosols more accurately in the RT algorithms.

We consider spectral modeling of the diffuse interstellar bands (DIBs). We focus on two aspects of DIB spectral modeling that are often overlooked, but significantly impact the interpretation of a spectral fit in terms of a potential molecular carrier. The first concerns ambiguities in the retrieved spectral parameters. Very different combinations of rotational temperature, transition symmetry, and spectroscopic parameters can yield nearly identical spectral fits. The second concerns the probability and effects of overlapping DIBs on spectral modeling. The high DIB spectral density, ~28 DIBs/Å, results in a significant overlap probability, ~30%. To exemplify these concerns, we model the spectral profile of the DIB λ6614. We use Gaussian fitting of λ6614 in order to show that it can be de-composed into two overlapping DIBs, λ6613.6, and λ6614.2. The spectral profiles of these DIBs can be fit more accurately than the fit obtained by treating λ6614 as a single DIB.

Striping effects, i.e., artifacts that vary systematically with the image column or row, may arise in hyperspectral or multispectral imagery from a variety of sources. One potential source of striping is a physical effect inherent in the measurement, such as a variation in viewing geometry or illumination across the image. More common sources are instrumental artifacts, such as a variation in spectral resolution, wavelength calibration or radiometric calibration, which can result from imperfect corrections for spectral "smile" or detector array nonuniformity. This paper describes a general method of suppressing striping effects in spectral imagery by referencing the image to a spectrally low-dimensional model. The destriping transform for a given column or row is taken to be affine, i.e., specified by a gain and offset. The image cube model is derived from a subset of spectral bands or principal components thereof. The general approach is effective for all types of striping, including broad or narrow, sharp or graduated, and is applicable to radiance data at all optical wavelengths and to reflectance data in the solar (visible through short-wave infrared) wavelength region. Some specific implementations are described, including a method for suppressing effects of viewing angle variation in VNIR-SWIR imagery.

We suggest that the diffuse interstellar bands (DIBs) arise from absorption lines of electronic transitions in molecular clusters primarily composed of a single molecule, atom, or ion (“seed”), embedded in a single-layer shell of H2 molecules. Less abundant variants of the cluster, including two seed molecules and/or a two-layer shell of H2 molecules, may also occur. The lines are broadened, blended, and wavelength-shifted by interactions between the seed and surrounding H2 shell. We refer to these clusters as contaminated H2 clusters (CHCs). We show that CHC spectroscopy matches the diversity of observed DIB spectral profiles and provides good fits to several DIB profiles based on a rotational temperature of 10 K. CHCs arise from ∼centimeter-sized, dirty H2 ice balls, called contaminated H2 ice macro-particles (CHIMPs), formed in cold, dense, giant molecular clouds (GMCs), and later released into the interstellar medium (ISM) upon GMC disruption. Attractive interactions, arising from Van der Waals and ion-induced dipole potentials, between the seeds and H2 molecules enable CHIMPs to attain centimeter-sized dimensions. When an ultraviolet (UV) photon is absorbed in the outer layer of a CHIMP, it heats the icy matrix and expels CHCs into the ISM. While CHCs are quickly destroyed by absorbing UV photons, they are replenished by the slowly eroding CHIMPs. Since CHCs require UV photons for their release, they are most abundant at, but not limited to, the edges of UV-opaque molecular clouds, consistent with the observed, preferred location of DIBs. An inherent property of CHCs, which can be characterized as nanometer size, spinning, dipolar dust grains, is that they emit in the radio-frequency region. We also show that the CHCs offer a natural explanation for the anomalous microwave emission feature in the ∼10–100 GHz spectral region.