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Electron affinity trend5/26/2023 ![]() ![]() The collisionally stabilized complex − has been reported, in low yield, in an IMS-MS experiment however, the highest yield of this product was observed at the highest drift field, which is at variance with expected behavior, if dissociation is occurring in the drift region.Ĭommercial ETDs are equipped with chlorocarbons, such as hexachloroethane, that have relatively low vapor pressures and are suitable for long-term unattended operation. (2) Cl − + TNT → TNT + Cl − ⁎ → HCl + TNT – H − Δ H o = – Δ GPA = − 74.9 kJ mol − 1 Time dependent external potential v ( r → ) = Non-Weizsäcker part of the kinetic energy VWN = Thomas-Fermi kinetic energy density T NW = Quantitative structure-toxicity relationship ρ ( r → ) = Quantitative structure-property relationship QSTR = Quantitative structure-activity relationship QSPR = Highest occupied molecular orbital HSAB = Generalized nonlinear Schrödinger equation HOMO = Hohenberg-Kohn-Sham universal functional f ( r → ) = Lowest unoccupied molecular orbital energy E xc =Įxchange-correlation energy functionals FF = Highest occupied molecular orbital energy ∈ LUMO = Variation of hardness with electron number DFT = This fact can be valuable when the EA is not as well-known as in the case of the boron atom.īecke three-parameter Lee-Yang-Parr functional = Therefore, the CI treatment leads to a result which is competitive with experiment and more advances theories. Indeed, as the nuclear charge is the same for the neutral atom and the anion, the electronic cusp effects represented by the interelectronic distance r 12 may cancel in the inner shell 1 and the same happens with relativistic and high relativistic effects. We look forward to more experimental data to provide benchmarks for our theoretical treatments.Ībbreviations: CCSDT, Coupled Cluster MC-DF, Multiconfigurational Dirac-Fock MC-DHF, Multiconfigurational Dirac–Hartree–Fock MP, Möller-Plesset perturbation theory MRCI, Multireference CI r12-MR-ACPF, explicitly correlated Multireference Averaged Coupled-Pair Functional. With the current very limited experimental data a relaxation correction of 0.3 eV instead of 0.6 eV appears more realistic. ![]() This suggests our estimates of the relaxation energies of the DNA bases were overestimated. Scherman have evidence that uracil should have a adiabatic EAs in the range 0 to 0.1 eV. No experimental value of an adiabatic EA has been reported for any nucleic acid base. These values are reported in Table 2 and are within experimental error of the calculated values of uracil, thymine and cytosine. 1998, 102, 6205 (errors are ± 0.05 eV).Įxperimental electron transfer spectroscopy values of the vertical EAs of the DNA bases have been recently measured by K. b The estimated adiabatic values are the EA(vert) plus 0.6 eV. Results of these calculations are reported in Table 2.Ī The vertical EA values reported in this table use D95v/6-31G* Koopmans EA (LUMO) in the fitted relation: EA (exp) = 0.8093EA(calc) + 1.727. The calculations employ tight basis sets which do not allow for electron detachment. The scaling is then applied to the Koopmans EAs for the DNA bases. These calculations scale HF calculations of Koopmans EA for a number of model systems to experimentally known negative electron affinities. To overcome this problem in our work we have employed an approximate technique for such species with some success. However, DFT codes are variational and also fail for species with negative electron affinities. Recently density functional methods (DFT) have had considerable success for prediction of EAs in a variety of systems. However, theoretical methods that do not consider scattering can not treat these systems directly. Temporary virtual orbital states are measured by electron transmission spectroscopy so experimental values exist for species with negative electron affinities. Further since molecular orbital calculations employ the Variation Principle and therefore seek the lowest energy state, calculations for species with negative electron affinities have the difficulty that the electron would be lost to the gas phase or a dipole bound state with large enough basis sets. Since uracil is predicted to have the highest electron affinity of all nucleic acid bases, all DNA bases should have negative vertical electron affinities. Only one experimental value of a vertical EA of a nucleic acid (uracil) has been reported and it is negative, i.e., unbound. ![]()
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