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Articles 31 - 33 of 33
Full-Text Articles in Physical Sciences and Mathematics
Studies Of Ngc 6720 With Calibrated Hst/Wfc3 Emission-Line Filter Images. Ii. Physical Conditions, C. R. O'Dell, Gary J. Ferland, W. J. Henney, M. Peimbert
Studies Of Ngc 6720 With Calibrated Hst/Wfc3 Emission-Line Filter Images. Ii. Physical Conditions, C. R. O'Dell, Gary J. Ferland, W. J. Henney, M. Peimbert
Physics and Astronomy Faculty Publications
We have performed a detailed analysis of the electron temperature and density in the Ring Nebula using the calibrated Hubble Space Telescope WFC3 images described in the preceding paper. The electron temperature (Te) determined from [NII] and [O III] rises slightly and monotonically toward the central star. The observed equivalent width (EW) in the central region indicates that Te rises as high as 13,000 K. In contrast, the low EWs in the outer regions are largely due to scattered diffuse Galactic radiation by dust. The images allowed determination of unprecedented small-scale variations in Te. …
Studies Of Ngc 6720 With Calibrated Hst/Wfc3 Emission-Line Filter Images. I. Structure And Evolution, C. R. O'Dell, Gary J. Ferland, W. J. Henney, M. Peimbert
Studies Of Ngc 6720 With Calibrated Hst/Wfc3 Emission-Line Filter Images. I. Structure And Evolution, C. R. O'Dell, Gary J. Ferland, W. J. Henney, M. Peimbert
Physics and Astronomy Faculty Publications
We have performed a detailed analysis of the Ring Nebula (NGC 6720) using Hubble Space Telescope WFC3 images and derived a new three-dimensional model. Existing high spectral resolution spectra played an important supplementary role in our modeling. It is shown that the Main Ring of the nebula is an ionization-bounded irregular non-symmetric disk with a central cavity and perpendicular extended lobes pointed almost toward the observer. The faint outer halos are determined to be fossil radiation, i.e., radiation from gas ionized in an earlier stage of the nebula when it was not ionization bounded. The narrowband WFC3 filters that isolate …
Calculated Vibrational Properties Of Ubisemiquinones, Hari P. Lamichhane, Gary Hastings
Calculated Vibrational Properties Of Ubisemiquinones, Hari P. Lamichhane, Gary Hastings
Physics and Astronomy Faculty Publications
Density functional theory has been used to calculate harmonic normal mode vibrational frequencies for unlabeled and isotopelabeled ubisemiquinones in both the gas phase and in several solvents. It is shown that four methoxy group conformations are likely to be present in solution at room temperature. Boltzmann weighted infrared and Raman spectra for the four conformers were calculated, and composite spectra that are the sum of the Boltzmann weighted spectra were produced. These composite spectra were compared to experimental FTIR and resonance Raman spectra, and it is shown that the calculated band frequencies, relative band intensities, and 13C and 18 …