Electron-impact vibrational excitation of cyclopropane

We report a very detailed test of the ab initio discrete momentum representation (DMR) method of calculating vibrational excitation of polyatomic molecules by electron impact, by comparison of its results with an extensive set of experimental data, covering the entire range of scattering angles from 10∘ to 180∘ and electron energies from 0.4 to 20 eV. The DMR calculations were carried out by solving the two-channel Lippmann-Schwinger equation in the momentum space, and the interaction between the scattered electron and the target molecule was described by exact static-exchange potential corrected by a density functional theory (DFT) correlation-polarization interaction that models target’s response to the field of incoming electron. The theory is found to quantitatively reproduce the measured spectra for all normal modes, even at the difficult conditions of extreme angles and at low energies, and thus provides full understanding of the excitation mechanism. It is shown that the overlap of individual vibrational bands caused by limited experimental resolution and rotational excitation must be properly taken into account for correct comparison of experiment and theory. By doing so, an apparent discrepancy between published experimental data could be reconciled. A substantial cross section is found for excitation of the non-symmetric HCH twisting mode ν 4 of A′′1 symmetry by the 5.5 eV A′2 resonance, surprisingly because the currently accepted selection rules predict this process to be forbidden. The DMR theory shows that the excitation is caused by an incoming electron in an f-wave of A′2 symmetry which causes excitation of the non-symmetric HCH twisting mode ν 4 of the A′′1 symmetry and departs in p- and f-waves of A′′2 symmetry

Influence of β β β β-Resorcylidene Aminoguanidine on Selected Metabolic Parameters and Antioxidant Status of Rats with Diabetes Mellitus

Summary We studied the effects of administration of β-resorcylidene aminoguanidine (RAG) to Wistar strain rats with experimental diabetes mellitus (DM) induced by streptozotocin. The effects studied included antioxidant levels in plasma and the liver, oxidative damage of lipids represented by the formation of substances reacting with thiobarbituric acid (TBARP) and selected biochemical indicators. The administration of RAG did not significantly affect antioxidant status of diabetic rats or hemoglobin glycation and plasma concentration of fructosamine. In diabetic rats, application of RAG decreased formation of TBARP in plasma but not in the liver. Moderate steatosis of liver and increased plasma levels of triacylglycerols in diabetic rats were significantly improved by application of RAG

Vibrational excitation of methane by slow electrons revisited: theoretical and experimental study

We have calculated and measured differential and integral cross sections for vibrationally inelastic scattering of electrons by methane molecules. The calculations were carried out using the discrete momentum representation (DMR) method. We solved the two-channel Lippmann–Schwinger equation in the momentum space. The interaction between the scattered electron and the target molecule is described by the exact static-exchange potential. Correlation–polarization forces were included by a simple local density functional theory potential of Perdew and Zunger (1981 Phys. Rev. B 23 5048). The cross sections calculated in this way agree very well with our measurement and with other more recent experimental data, but are larger than some older experimental and theoretical results

A multireference coupled-cluster potential energy surface of diazomethane, CH2N2

The intrinsically multireference dissociation of the C-N bond in ground-state diazomethane (CH2N2) at different angles has been studied with the multireference Brillouin-Wigner coupled-cluster singles and doubles (MRBWCCSD) method. The morphology of the calculated potential energy surface (PES) in Cs symmetry is similar to a multireference perturbational (CASPT3) PES. The MRBWCCSD/cc-pVTZ H2C-N2 dissociation energy with respect to the asymptotic CH2(ā 1A1) + N2(X1∑g +) products is De = 35.9 kcal/mol, or a zero-point corrected D 0 = 21.4 kcal/mol with respect to the ground-state CH 2(X̃3B1) + N2(X 1∑g+) fragments. © 2005 American Chemical Society