Simple analysis of the thermodynamic properties of the one-component plasma

The one-component plasma model describing a fluid of identically charged point-like ions moving in a uniform continuum background charge density neutralizing the total system is a chemically relevant special case of the primitive models used in theories of electrolyte solutions. It poses, due to its lack of hard-sphere repulsion, an unusual and particularly difficult problem for both the traditional Debye—H$\text{u}$ckel theory and the modern pair correlation theories. We show that the gross error of the Debye—H$\text{u}$ckel predictions for thermodynamic properties at high coupling strength (as compared to Monte Carlo simulation results) can be effectively removed by an extremely simple modification of the theory based on the recognition that the exponential particle density must be truncated close to the ion so as not to become negative.     

Proton and deuterium NMR of hydrogen bonds: Relationship between isotope effects and the hydrogen bond potential

The difference in chemical shift between hydrogen bonded protons and deuterons has been examined both theoretically and experimentally. It is shown that valuable information about the hydrogen bond potential can be extracted from this isotope effect on chemical shifts.     

PECT model analysis and predictions of experimental collisional energy transfer probabilities P(E',E) and moments <DeltaE> for azulene and biphenylene

Experimental collisional energy transfer data from kinetically controlled selective ionization (KCSI) and ultraviolet absorption (UVA) experiments are analyzed in the framework of the partially ergodic collision theory (PECT). Collisions of azulene and biphenylene with different colliders are investigated as case studies. The downward wings of the P(E',E) energy transfer distributions obtained from the PECT model are fitted to the recently introduced "variable-shape"-exponential 3-parameter functional form of P(E',E) obtained from KCSI experiments, P(E',E) proportional, variant exp[-{(E - E')/(C(0) + C(1)E)}(Y)]. The PECT model is able to reproduce the characteristic dependence of the KCSI "shape parameter" Y on the choice of collider, the energy dependent width of the KCSI P(E',E) distributions, described by alpha(E) = C(0) + C(1)E, and the temperature dependence of the UVA data above room temperature. The statistical approach of PECT obviously captures the essence of large molecule energy transfer at chemically significant energies without the need of knowing specific features of the detailed collision dynamics. It therefore shows promise for predicting the shape of P(E',E) in master equation kernels for larger molecules.     

Generation of random processes for fatigue testing

In fatigue testing there is a need to generate multivariate random processes meeting certain conditions on distributions, crossing properties and regularity. In this paper it is demonstrated how these conditions can be satisfied. The required process is generated by a random time deformation working on a Gaussian process.     

Bromine-bromine energy transfer by binary collisions

The collisional energy transfer between a highly excited bromine molecule and a non-reactive monatomic (Ar or Br) or diatomic (Br₂) medium has been investigated by binary trajectory calculations over a wide range of medium temperatures and internal energies of the reactant molecule. The efficiency of the energy transfer is compared with expectations based on simple statistical approximations used in unimolecular reaction rate theory. Large deviations are found, particularly with respect to the contributions made by different types of degrees of freedom and to the dependence on the internal energy of the reactant molecule. Transfer to or from vibrational degrees of freedom appears to be very inefficient. Translational energy is most readily transferred. The rate coefficient for energy transfer appears to decrease with increasing internal energy in most cases.     

Calculation of photoionization cross sections by the absorbing boundary method

A new method for the calculation of quantum state decay rates, the absorbing boundary method (ABM), has recently been developed. In this talk the general form of the ABM will be outlined. The pseudo bound state approach to the calculation of continuum rates such as photoionization cross sections and used by Langhoff and coworkers will be briefly reviewed and shown to lack precision in the absence of information about the line widths and shapes of the pseudo bound states. It will then be noted that the ABM can be used to construct a rigorous new approach to the calculation of photoionization cross sections incorporating the necessary lifetime information for the pseudo bound states while still allowing the computation to be carried out by bound state procedures.     

Calculation of atomic and molecular photoionization cross sections using the ground state inversion potential method

Calculations of atomic photoionization cross sections to near Hartree-Fock accuracy can be achieved very simply if the non-local Hartree-Fock potential experienced by the photoelectron is replaced by a local potential obtained by inversion of the corresponding ground state orbital. Subshell cross sections for atomic photoionizatim for representative atoms in the range 0–1500 eV calculated in this way are in good general agreement with Hartree-Fock values and with experiment. The extension to molecular systems and the use of an independent atomic centre approach to calculation of molecular photoionization cross sections at low photon energies is outlined.