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Articles 1 - 6 of 6
Full-Text Articles in Physics
A Zero Point And Accidental Errors For Published Values Of [Fe/H] For Cool Giants, B. J. Taylor
A Zero Point And Accidental Errors For Published Values Of [Fe/H] For Cool Giants, B. J. Taylor
Faculty Publications
This paper is one of a series based on published values of [Fe/H] for late-type evolved stars. Only values of [Fe/H] from high-dispersion spectroscopy or related techniques are used. The narrative in this paper begins at a point where mean values of [Fe/H] have been derived for xiVir, alphaBoo, betaGem, and the Hyades giants. By using these stars as standard stars when necessary, a zero-point data base is assembled. This data base is then expanded into its final version by correcting and adding additional data in a step-by-step process. As that process proceeds, data comparisons are used to establish rms …
An Analysis Of Temperature Dependent Photoluminescence Line Shapes In Ingan, John S. Colton, K. L. Teo, P. Y. Yu, E. R. Weber, M. F. Li, W. Lui, K. Uchida, H. Tokunaga, N. Akutsu, K. Matsumoto
An Analysis Of Temperature Dependent Photoluminescence Line Shapes In Ingan, John S. Colton, K. L. Teo, P. Y. Yu, E. R. Weber, M. F. Li, W. Lui, K. Uchida, H. Tokunaga, N. Akutsu, K. Matsumoto
Faculty Publications
Photoluminescence (PL) line shapes in InGaN multiple quantum well structures have been studied experimentally and theoretically between 10 and 300 K. The higher temperature PL spectra can be fitted qualitatively with a thermalized carrier distribution and a broadened joint-density-of-states. The low temperature PL line shapes suggest that carriers are not thermalized, as a result of localization by band-gap fluctuations. We deduce a localization energy of ~7 meV as compared with an activation energy of ~63 meV from thermal quenching of the PL intensity. We thus conclude that this activation energy and the band-gap fluctuation most likely have different origins.
Catalogs Of Temperatures And [Fe/H] Averages For Evolved G And K Stars, B. J. Taylor
Catalogs Of Temperatures And [Fe/H] Averages For Evolved G And K Stars, B. J. Taylor
Faculty Publications
A catalog of mean values of [Fe/H] for evolved G and K stars is described. The zero point for the catalog entries has been established by using differential analyses. Literature sources for those entries are included in the catalog. The mean values are given with rms errors and numbers of degrees of freedom, and a simple example of the use of these statistical data is given. For a number of the stars with entries in the catalog, temperatures have been determined. A separate catalog containing those data is briefly described.
Thermal Equilibrium Of Warm Clouds Of Charge With Small Aspect Ratio, Deborah L. Paulson, Ross L. Spencer
Thermal Equilibrium Of Warm Clouds Of Charge With Small Aspect Ratio, Deborah L. Paulson, Ross L. Spencer
Faculty Publications
Global thermal equilibrium computations are presented for non-neutral plasmas whose radial size is much larger than their axial thickness. Axial and radial density profiles are computed for both ideal and nonideal Penning trap fields. Simple results are obtained in the limits of both low and high central density. Comparison is made to the grid calculations of Mason et al. [Phys. Plasmas 3 (5), 1502 (1996)].
Time-Resolved Studies Of Ultracold Ionizing Collisions, Scott D. Bergeson, C. Orzel, S. Kulin, S. L. Rolston
Time-Resolved Studies Of Ultracold Ionizing Collisions, Scott D. Bergeson, C. Orzel, S. Kulin, S. L. Rolston
Faculty Publications
Using 40 ns laser pulses, we probe the real-time dynamics of ultracold ionizing collisions in metastable xenon. We time resolve both shielding and enhancement effects, and observe the production of Xe2^+ molecular ions through associative ionization. We estimate the rate of molecule formation in excited-state collisions, and directly measure the role of both flux enhancement and excited state survival in the collisional enhancement process. Conceptually simple theoretical models are used to predict the dynamics of the collisional shielding.
Measurement Of The He Ground State Lamb Shift Via The Two-Photon 1 1S-2 1S Transition, Scott D. Bergeson, A. Balakrishnan, K. G. H. Baldwin, T. B. Lucatorto, J. P. Marangos, T. J. Mcilrath, T. T. O'Brian, S. L. Rolston, C. J. Sansonetti, Jesse Wen, N. Westbrook, C. H. Cheng, E. E. Eyler
Measurement Of The He Ground State Lamb Shift Via The Two-Photon 1 1S-2 1S Transition, Scott D. Bergeson, A. Balakrishnan, K. G. H. Baldwin, T. B. Lucatorto, J. P. Marangos, T. J. Mcilrath, T. T. O'Brian, S. L. Rolston, C. J. Sansonetti, Jesse Wen, N. Westbrook, C. H. Cheng, E. E. Eyler
Faculty Publications
We have extended two-photon Doppler-free spectroscopy to the vacuum ultraviolet spectral region, to accurately measure the He 11S-21S transition at 120 nm. Our result is 4984872315(48) MHz. This yields a ground state Lamb shift of 41104(48) MHz, in fair agreement with theory and other experiments. This approach has the potential for significantly better accuracy once improvements in the laser and the wavelength metrology are implemented.