Moderate spectral resolution observations of 3 micron absorption features in highly obscured objects

The 3 micron absorption spectra of sources seen in or behind molecular clouds generally show a variety of absorption features. Three separate absorptions are used to explain these features. The cooled-grating array spectrometer (CGAS) at the NASA Infrared Telescope Facility was used to obtain spectra of the late-type mass-loss star OH 0739-12 and the protostars MonR2 IRS-2 and IRS-3 (solid circles). The differences between the spectra are discussed

Spectral components at visual and infrared wavelengths in active galactic nuclei

Aperture-dependent infrared photometry of active galactic nuclei are presented which illustrate the importance of eliminating starlight of the galaxy in order to obtain the intrinsic spectral distribution of the active nuclei. Separate components of emission are required to explain the infrared emission with a spectral index of alpha approx = 2 and the typical visual-ultraviolet continuum with alpha approx = 0.3 (where F(nu) varies as nu(sup-alpha). Present evidence does not allow unique determination of the appropriate mechanisms, but the characteristics of each are discussed

Lattice-form dependent orbital shape and charge disproportionation in charge- and orbital-ordered manganites

The orbital shapes and charge disproportionations at nominal Mn$^{3+}$ and Mn$^{4+}$ sites for the charge- and orbital-ordered phases have been studied on half-doped manganites Pr(Sr$_{0.1}$Ca$_{0.9}$)$_2$Mn$_2$O$_7$ and Eu$_{0.5}$Ca$_{1.5}$MnO$_4$ with double-layer and single-layer Mn-O networks, respectively, by means of x-ray structural analyses, in comparison with Pr$_{0.5}$Ca$_{0.5}$MnO$_3$ with the pseudo cubic network. In a single-layer Eu$_{0.5}$Ca$_{1.5}$MnO$_4$ system, the ($y^2-z^2$)/($z^2-x^2$)-type orbital shape is observed, while the ($3y^2-r^2$)/($3x^2-r^2$)-type orbital shape in a pseudo cubic Pr$_{0.5}$Ca$_{0.5}$MnO$_3$ system. In a double-layer Pr(Sr$_{0.1}$Ca$_{0.9}$)$_2$Mn$_2$O$_7$ system, the orbital shape is found to undergo a large change upon thermally induced rotation of orbital stripe. Furthermore, clear charge disproportionation is observed for the pseudo cubic and double-layer systems, while not in the single-layer system. These results indicate that the orbital shape and charge disproportionation are sensitive to the dimension of Mn-O network.Comment: 12 page, 5 figures, 11 table

Low-dimensional chaos induced by frustration in a non-monotonic system

We report a novel mechanism for the occurrence of chaos at the macroscopic level induced by the frustration of interaction, namely frustration-induced chaos, in a non-monotonic sequential associative memory model. We succeed in deriving exact macroscopic dynamical equations from the microscopic dynamics in the case of the thermodynamic limit and prove that two order parameters dominate this large-degree-of-freedom system. Two-parameter bifurcation diagrams are obtained from the order-parameter equations. Then we analytically show that the chaos is low-dimensional at the macroscopic level when the system has some degree of frustration, but that the chaos definitely does not occur without the frustration.Comment: 2 figure

Stark deceleration of lithium hydride molecules

We describe the production of cold, slow-moving LiH molecules. The molecules are produced in the ground state using laser ablation and supersonic expansion, and 68% of the population is transferred to the rotationally excited state using narrowband radiation at the rotational frequency of 444GHz. The molecules are then decelerated from 420m/s to 53m/s using a 100 stage Stark decelerator. We demonstrate and compare two different deceleration modes, one where every stage is used for deceleration, and another where every third stage decelerates and the intervening stages are used to focus the molecules more effectively. We compare our experimental data to the results of simulations and find good agreement. These simulations include the velocity dependence of the detection efficiency and the probability of transitions between the weak-field seeking and strong-field seeking quantum states. Together, the experimental and simulated data provide information about the spatial extent of the source of molecules. We consider the prospects for future trapping and sympathetic cooling experiments.Comment: 14 pages, 6 figures; minor revisions following referee suggestion

Limit on the CH4/CO ratio in Comet Levy (1990c) and comparisons with other comets

Near-infrared observations of comet Levy (1900c) were made on UT 4.3 and 5.3 Sep. 1990 from the United Kingdom Infrared Telescope on Mauna Kea. A scanning Fabry-Perot interferometer in combination with a cooled grating spectrometer was used to make a sensitive search for fluorescent emission from the v zub 3 band of CH4 near lambda approx. 3.3 microns. If CH4 is a parent molecule released directly from the nucleus, then the 3 sigma limit on its abundance is CH4/H2O approx. less than 0.0031, assuming that the kinetic temperature of the inner coma is approx. 50 K and that the CH4 spin species are equilibrated at a temperature approx. greater than 50 K. Since International Ultraviolet Explorer (IUE) observations of CO in Levy indicate that CO/H2O approx. 0.04 (Feldman et al.), researchers find that CH4/CO approx. less than 0.1. Infrared spectroscopic searches for CH4 in Comet Halley also yielded no positive detections; the more sensitive upper limit from the latter observations is CH4/H2O approx. less than 0.002. Since CO/H2O approx. 0.05 in Halley (not including the extended source of CO), the upper limits on the CH4/CO ratios are almost identical for comets Levy and Halley. A marginal infrared detection of the CH4 v sub 3 band in comet Wilson yielded CH4/H2O approx. 0.01 to 0.05 (Larson et al.), but there was no positive detection of CO. If the identification of the feature in the infrared spectrum of comet Wilson is correct, then that would indicate a very high CH4/CO ratio in this comet

A strong 3.4 micron emission feature in comet Austin 1989c1

High resolution 2.8-4.0 micron spectra of the 'new' comet Austin 1989c1, taken on 15-16 May 1990 confirm the presence of the broad emission features around 3.4 and 3.52 micron seen in a number of bright comets and ascribed to organic material. Both the 3.4 micron band strength and the 3.52/3.36 micron flux ratios are among the largest so far observed. The data are consistent with the relationship between band strength and water production rate that was recently derived. Excess emission at 3.28 and 3.6 micron cannot be unambiguously identified as features due to the poor signal-to-noise ratio

A search for varying fundamental constants using Hz-level frequency measurements of cold CH molecules

Many modern theories predict that the fundamental constants depend on time, position, or the local density of matter. We develop a spectroscopic method for pulsed beams of cold molecules, and use it to measure the frequencies of microwave transitions in CH with accuracy down to 3 Hz. By comparing these frequencies with those measured from sources of CH in the Milky Way, we test the hypothesis that fundamental constants may differ between the high and low density environments of the Earth and the interstellar medium. For the fine structure constant we find \Delta\alpha/\alpha = (0.3 +/- 1.1)*10^{-7}, the strongest limit to date on such a variation of \alpha. For the electron-to-proton mass ratio we find \Delta\mu/\mu = (-0.7 +/- 2.2) * 10^{-7}. We suggest how dedicated astrophysical measurements can improve these constraints further and can also constrain temporal variation of the constants.Comment: 8 pages, 3 figure

The abundances of ethane to acetylene in the atmospheres of Jupiter and Saturn

The present determination of the stratospheric abundances of ethane and acetylene on Jupiter and Saturn on the basis of IR spectra near 780/cm uses atmospheric models whose thermal and density profiles have constant mixing ratios. The ratio of ethane to acetylene is noted to be insensitive to model atmosphere assumptions; it is 55 + or - 31 for Jupiter and 23 + or - 12 where model mixing ratios are uniform. Atmospheric model density profiles adapted from theoretical photochemical models are noted to also yield a higher ethane/acetylene ratios for Jupiter