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Photodissociation spectroscopy and dynamics of free radicals, clusters, and ions

Description: The photodissociation spectroscopy and dynamics of free radicals and ions is studied to characterize the dissociative electronic states in these species. To accomplish this, a special method of radical production, based on the photodetachment of the corresponding negative ion, has been combined with the technique of fast beam photofragment translational spectroscopy. The photofragment yield as a function of photon energy is obtained, mapping out the dissociative and predissociative electronic s… more
Date: December 16, 1999
Creator: Hyeon, Choi
Partner: UNT Libraries Government Documents Department
open access

Growth of a Au-Ni-Sn intermetallic compound on the solder-substrate interface after aging

Description: Au/Ni metallization has become increasingly common in microelectronic packaging when Cu pads are joined with Pb-Sn solder. The outermost Au layer serves to protect the pad from corrosion and oxidation and the Ni layer provides a diffusion barrier to inhibit detrimental growth of Cu-Sn intermetallics. As a result of reflowing eutectic Pb-Sn on top of Au/Ni metallization, the as-solidified joints have AuSn{sub 4} precipitates distributed throughout the bulk of the solder joint, and Ni{sub 3}Sn{su… more
Date: December 16, 1999
Creator: Minor, Andrew M. & Morris, J. W., Jr.
Partner: UNT Libraries Government Documents Department
open access

X-ray absorption spectroscopy on the calcium cofactor to the manganese cluster in photosynthetic oxygen evolution

Description: Along with Mn, calcium and chloride ions are necessary cofactors for oxygen evolution in Photosystem II (PS II). To further test and verify whether Ca is close to the Mn cluster, the authors substituted strontium for Ca and probed from the Sr point of view for any nearby Mn. The extended X-ray absorption fine structure (EXAFS) of Sr-reactivated PS II indicates major differences between the intact and NH{sub 2}OH-treated samples. In intact samples, the Fourier transform of the Sr EXAFS shows a F… more
Date: December 16, 1999
Creator: Cinco, Roehl M.
Partner: UNT Libraries Government Documents Department
open access

Anion photoelectron spectroscopy of radicals and clusters

Description: Anion photoelectron spectroscopy is used to study free radicals and clusters. The low-lying {sup 2}{Sigma} and {sup 2}{Pi} states of C{sub 2n}H (n = 1--4) have been studied. The anion photoelectron spectra yielded electron affinities, term values, and vibrational frequencies for these combustion and astrophysically relevant species. Photoelectron angular distributions allowed the author to correctly assign the electronic symmetry of the ground and first excited states and to assess the degree o… more
Date: December 16, 1999
Creator: Travis, Taylor R.
Partner: UNT Libraries Government Documents Department
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