A high-Resolution Catalog of Cometary Emission Lines

Using high-resolution spectra obtained with the Hamilton echelle spectrograph at Lick Observatory, we have constructed a catalog of emission lines observed in comets Swift-Tuttle and Brorsen-Metcalf. The spectra cover the range between 3800 Å and 9900 Å with a spectral resolution of λ/Δλ~42000. In the spectra, we catalog 2997 emission lines of which we identify 2438. We find cometary lines due to H, O, C_2, CN, NH_2, C_3, H_2O^+, CH, and CH^+. We list 559 unidentified lines compiled from the two spectra and comment on possibilities for their origins

New T=1 effective interactions for the f5/2 p3/2 p1/2 g9/2 model space; Implications for valence-mirror symmetry and seniority isomers

New shell model Hamiltonians are derived for the T=1 part of the residual interaction in the f5/2 p3/2 p1/2 g9/2 model space based on the analysis and fit of the available experimental data for 57Ni-78Ni isotopes and 77Cu-100Sn isotones. The fit procedure, properties of the determined effective interaction as well as new results for valence-mirror symmetry and seniority isomers for nuclei near 78Ni and 100Sn are discussed.Comment: 4 pages, 5 figure

Non-detection of the OH Meinel system in comet P/Swift-Tuttle

We report a search for emissions from the OH Meinel system in high-resolution near-infrared spectra of comet P/Swift-Tuttle. Because of the large cometary heliocentric velocity and high resolution of the spectrograph, the cometary lines should be well separated from the bright OH sky lines. Contrary to the findings of Tozzi et al. (1994) - who report seeing cometary OH at intensities comparable to the sky emissions in their low-resolution spectra - we find no OH in these spectra with an upper limit of 5% the value of the night sky lines. The non-detection of these cometary lines is consistent with theoretical calculations of expected emission strengths from prompt and fluorescent emission from cometary OH

New effective interaction for pfpf-shell nuclei and its implications for the stability of the NN=ZZ=28 closed core

The effective interaction GXPF1 for shell-model calculations in the full $pf$ shell is tested in detail from various viewpoints such as binding energies, electro-magnetic moments and transitions, and excitation spectra. The semi-magic structure is successfully described for $N$ or Z=28 nuclei, $^{53}$Mn, $^{54}$Fe, $^{55}$Co and $^{56,57,58,59}$Ni, suggesting the existence of significant core-excitations in low-lying non-yrast states as well as in high-spin yrast states. The results of $N=Z$ odd-odd nuclei, $^{54}$Co and $^{58}$Cu, also confirm the reliability of GXPF1 interaction in the isospin dependent properties. Studies of shape coexistence suggest an advantage of Monte Carlo Shell Model over conventional calculations in cases where full-space calculations still remain too large to be practical.Comment: 29pages, 26figures, to be published in Physical Review

Two Modes of Magnetization Switching in a Simulated Iron Nanopillar in an Obliquely Oriented Field

Finite-temperature micromagnetics simulations are employed to study the magnetization-switching dynamics driven by a field applied at an angle to the long axis of an iron nanopillar. A bi-modal distribution in the switching times is observed, and evidence for two competing modes of magnetization-switching dynamics is presented. For the conditions studied here, temperature $T = 20$ K and the reversal field 3160 Oe at an angle of 75$^\circ$ to the long axis, approximately 70% of the switches involve unstable decay (no free-energy barrier) and 30% involve metastable decay (a free-energy barrier is crossed). The latter are indistinguishable from switches which are constrained to start at a metastable free-energy minimum. Competition between unstable and metastable decay could greatly complicate applications involving magnetization switches near the coercive field.Comment: 19 pages, 7 figure

Reactions of Na/plus/, K/plus/, and Ba/plus/ ions with O2, NO, and H2O molecules

Investigating ion molecule reactions of sodium, potassium, and barium ions with oxygen, nitric oxide, and water in drift tube mass spectromete

Discovery of Temperate Latitude Clouds on Titan

Until now, all the clouds imaged in Titan's troposphere have been found at far southern latitudes (60°-90° south). The occurrence and location of these clouds is thought to be the result of convection driven by the maximum annual solar heating of Titan's surface, which occurs at summer solstice (2002 October) in this south polar region. We report the first observations of a new recurring type of tropospheric cloud feature, confined narrowly to ~40° south latitude, which cannot be explained by this simple insolation hypothesis. We propose two classes of formation scenario, one linked to surface geography and the other to seasonally evolving circulation, which will be easily distinguished with continued observations over the next few years