Physical Sciences and Mathematics Commons^™

Hydrogeochemical Aspects Of Surface Mine Reclamation In The Northern Great Plains, Gerald H. Groenewold, Robert D. Koob

Office of the Provost Scholarship

Studies of several coal-mining sites in western North Dakota have resulted in the development of a hydrogeochemical model which accounts for the observed chemical characteristics of subsurface water in undisturbed settings. Critical hydrogeochemical processes include sulfide oxidation, gypsum precipitation and dissolution, carbonate mineral dissolution and cation exchange.

In the semi-arid climate of western North Dakota, the near-surface several meters of the landscape is constantly subjected to alternate wetting/drying. This mechanism is the key to hydrogeochemical evolution of both pore water in the rooting zone and subsurface water that eventually reaches the water table.

Recent refinements in the hydrogeochemical model have …

Excited States And Photochemistry Of Saturated Molecules, Patrick M. Saatzer, Robert D. Koob, Mark S. Gordon

Office of the Provost Scholarship

The molecular structures and bond energies in the low-lying excited states of n-alkanes from methane to n-pentane are investigated using the semi-empirical INDO method with configuration interaction. In general the calculated geometries and bond energies are consistent with the known threshold photochemistry of these molecules, the only exception being the prediction of vicinal (rather than geminal) elimination of H₂ in ethane. It appears that INDO overestimates the amount of angular distortion in these excited states.

The Photolysis Of Propane At 123.6 Nm, James H. Vorachek, Robert D. Koob

Office of the Provost Scholarship

Propane has been photolyzed at 123.6 nm, in the presence and absence of O₂, at pressures from 2–380 Torr. All products except ethane exhibit a pressure dependence which is attributed to secondary dissociation of the primary fragments, H₂, CH₄, C₂H₄, and C₃H₆. It is assumed that the range of energies carried by these fragments is broad enough that some will not dissociate even at low pressures while others of the same species cannot be stabilized even at high pressures. An internally consistent analysis rationalizes the entire …

Radiolysis Of Liquid Propane: Radical Reactions, Robert D. Koob, Larry Kevan

Office of the Provost Scholarship

The radical reactions in the liquid phase γ-radiolysis of propane have been studied from –130 to 35°C and compared with the gas-phase radiolysis at 35°C. Oxygen was used as a scavenger to separate thermal radical yields, and effects of phase and temperature on the radical yields were assessed. The gas-liquid phase change(a) decreases total decomposition by about 14%,(b) increases disproportionation/combination (D/C) ratios for all radicals by 30% and (c) decreases the isopropyl/n-propyl radical ratio. The decrease in liquid temperature (a) changes the predominant reaction of H atoms from abstraction from propane to addition to product propylene below –78°C at doses …