Free-ion interactions

Crystal field effects are of the order of the free ion interaction thus they cannot be treated as a small perturbation as in the lanthanides. Whereas the crystal field splitting in the oxidation state +3 is comparable to that for the lanthanides, it is significantly increased in the progression... 

Calculated from parameters of table 3 including free ion interactions. Wave functions are not renormalized to 1. 

Mironov and Rosov (I992a,b) recently worked out a many-electron, semi-empirical crystal field calculation for the f" shells, where the valence subsystem of the f-cluster is treated by a MO-LCAO method while the f" free-ion interactions are described by empirical parameters. 

Most potentiometric electrodes are selective for only the free, uncomplexed analyte and do not respond to complexed forms of the analyte. Solution conditions, therefore, must be carefully controlled if the purpose of the analysis is to determine the analyte s total concentration. On the other hand, this selectivity provides a significant advantage over other quantitative methods of analysis when it is necessary to determine the concentration of free ions. For example, calcium is present in urine both as free Ca + ions and as protein-bound Ca + ions. If a urine sample is analyzed by atomic absorption spectroscopy, the signal is proportional to the total concentration of Ca +, since both free and bound calcium are atomized. Analysis with a Ca + ISE, however, gives a signal that is a function of only free Ca + ions since the protein-bound ions cannot interact with the electrode s membrane. 

The first simulation studies of full double layers with molecular models of ions and solvent were performed by Philpott and coworkers [51,54,158] for the NaCl solution, using the fast multipole method for the calculation of Coulomb interactions. The authors studied the screening of a negative surface charge by free ions in several highly concentrated NaCl solutions. A combination of (9-3) LJ potential and image charges was used to describe the metal surface. 

The nature of this interaction is not yet clear, but there is no doubt that this is a manifestation of a polymer-monomer interaction, typical of PCSs. The process of polymerization of phenylacetylene on free ions is characterized by the 6th order in initiator and monomer and has an activation energy of=25 kJ/mol (6 kcal/mol). 

The electrostatic and spin-orbit parameters for Pu + which we have deduced are similar to those proposed by Conway some years ago (32). However, inclusion of the crystal-field interaction in the computation of the energy level structure, which was not done earlier, significantly modifies previous predictions. As an approximation, we have chosen to use the crystal-field parameters derived for CS2UCI6 (33), Table VII, which together with the free-ion parameters lead to the prediction of a distinct group of levels near 1100 cm-. Of course a weaker field would lead to crystal-field levels intermediate between 0 and 1000 cm-1. Similar model calculations have been indicated in Fig. 8 for Nplt+, Pu1 "1 and Amlt+ compared to the solution spectra of the ions. For Am t+ the reference is Am4" in 15 M NHhF solution (34). 

The assumption of a large crystal-field interaction for Pu5+ spectra makes it necessary to conclude that while certain aspects of earlier free-ion estimates (37) are valid, the "assignment" of free-ion states to observed absorption bands was premature. Much of the structure must be due to crystal-field components of many free-ion groups that overlap in energy or to vibronic satellites similar to those encountered in CS2UCI6 (33). Thus, while the present computations would agree with earlier work in interpreting the levels observed in... 

The origin of the dependencies of AAg on rion can be rationalized in the following way. When the smaller metals are bound to the enzyme, the free energy of ij/2 will be lowered considerably more than that of the transition state (as well as i//3) since in the former the OH " ion is free to interact with or ligate the metal, while it is becoming partially bound to the 5 -P atom at the transition state with accompanying charge delocalization. On the other... 

Term wavefunctions describe the behaviour of several electrons in a free ion coupled together by the electrostatic Coulomb interactions. The angular parts of term wavefunctions are determined by the theory of angular momentum as are the angular parts of one-electron wavefunctions. In particular, the angular distributions of the electron densities of many-electron wavefunctions are intimately related to those for orbitals with the same orbital angular momentum quantum number that is. 

Rozanska, X. Chipot, C., Modeling ion-ion interaction in proteins a molecular dynamics free energy calculation of the guanidinium-acetate association, J. Chem. Phys. 2000, 112, 9691-9694. 

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