In the past, basis sets for use in correlated molecular calculations have largely been taken from single configuration calculations. Recently, Almlof, Taylor, and co‐workers have found that basis sets of natural orbitals derived from correlated atomic calculations (ANOs) provide an excellent description of molecular correlation effects. We report here a careful study of correlation effects in the oxygen atom, establishing that compact sets of primitive Gaussian functions effectively and efficiently describe correlation effects i f the exponents of the functions are optimized in atomic correlated calculations, although the primitive (s p) functions for describing correlation effects can be taken from atomic Hartree–Fock calculations i f the appropriate primitive set is used. Test calculations on oxygen‐containing molecules indicate that these primitive basis sets describe molecular correlation effects as well as the ANO sets of Almlof and Taylor. Guided by the calculations on oxygen, basis sets for use in correlated atomic and molecular calculations were developed for all of the first row atoms from boron through neon and for hydrogen. As in the oxygen atom calculations, it was found that the incremental energy lowerings due to the addition of correlating functions fall into distinct groups. This leads to the concept of c o r r e l a t i o n c o n s i s t e n t b a s i s s e t s, i.e., sets which include all functions in a given group as well as all functions in any higher groups. Correlation consistent sets are given for all of the atoms considered. The most accurate sets determined in this way, [5s4p3d2f1g], consistently yield 99% of the correlation energy obtained with the corresponding ANO sets, even though the latter contains 50% more primitive functions and twice as many primitive polarization functions. It is estimated that this set yields 94%–97% of the total (HF+1+2) correlation energy for the atoms neon through boron.

Gaussian basis sets for use in correlated molecular calculations. I. The atoms boron through neon and hydrogen

Chemistry has its origins as a quantitative science in the careful weighing of products and reactants by Lavoisier and his followers beginning some 200 years ago. Ever since then, the constantly evolving gravimetric balance has been a faithful servant of the laboratory chemist and has played a major role in developing the analytical methods that are the foundation of contemporary chemical science. Perhaps the ultimate stage in the evolution of that balance is represented by the modern mass spectrometer. It is able to determine with high precision the masses of individual atoms and molecules by transforming them into ions and measuring the response of their trajectories in vacuo to various combinations of electric and magnetic fields. Clearly, the sine qua non of such mass determination is the transformation of analyte atoms and molecules from their initial state in a sample to ions in vacuo ready for ”weighing.” Over the years, ingenious investigators have produced a variety of methods for achieving this transformation. One of them, electrospray ( E S ) ionization, has recently shown itself capable of producing intact ions, with multiple charges, from remarkably large, complex, and fragile parent species. Our assignment here is to review what has thus far been learned about this still uncommon technique and what it seems able to offer practitioners of mass spectrometric analysis. Our approach will be to set forth the present state of the ES ionization art in terms of a sort of menu of its procedures, processes, performance, and promise. Until very recently we have been almost the only group that has worked with ES ionization since the pioneering efforts of Malcolm Dole (1) some 20 years ago. Consequently, this review is more tutorial than most. Moreover, it may seem like a cook book that is overly preoccupied with the authors’ own culinary adventures. The reasoil is that many of the dishes to be described were first tried out in our own kitchen. Therefore, we earnestly urge the reader to remember what every gourmet knows: the piquancy of any dish on a bill of fare is due much less to its ingredients than to the skill of the chef whc. prepares it.

Electrospray ionization–principles and practice

Mise au point. Theorie des effets de couplage vibronique multimodes. Probleme a 2 etats. Couplage vibronique mettant en jeu des modes et des etats degeneres. Effets du couplage vibronique multimodes en spectroscopie. Comportement statistique des niveaux d'energie vibroniques. Intersections coniques et evolution temporelle de la fluorescence

Multimode molecular dynamics beyond the Born-Oppenheimer approximation

Handbook of SiC properties for fuel performance modeling

During the last few years, transition metal oxides (TMO) such as molybdenum tri-oxide (MoO3), vanadium pent-oxide (V2O5) or tungsten tri-oxide (WO3) have been extensively studied because of their exceptional electronic properties for charge injection and extraction in organic electronic devices. These unique properties have led to the performance enhancement of several types of devices and to a variety of novel applications. TMOs have been used to realize efficient and long-term stable p-type doping of wide band gap organic materials, charge-generation junctions for stacked organic light emitting diodes (OLED), sputtering buffer layers for semi-transparent devices, and organic photovoltaic (OPV) cells with improved charge extraction, enhanced power conversion efficiency and substantially improved long term stability. Energetics in general play a key role in advancing device structure and performance in organic electronics; however, the literature provides a very inconsistent picture of the electronic structure of TMOs and the resulting interpretation of their role as functional constituents in organic electronics. With this review we intend to clarify some of the existing misconceptions. An overview of TMO-based device architectures ranging from transparent OLEDs to tandem OPV cells is also given. Various TMO film deposition methods are reviewed, addressing vacuum evaporation and recent approaches for solution-based processing. The specific properties of the resulting materials and their role as functional layers in organic devices are discussed.

Transition Metal Oxides for Organic Electronics: Energetics, Device Physics and Applications

The sublimation of hexagonal SiC has been studied under equilibrium conditions The predominant gaseous species above SiC are Si, SiC2, and Si2C By combining the heat of formation of gaseous Si from solid SiC and the known standard heat of formation of SiC, a value of 113 kcal/g atom is obtained for the heat of sublimation of Si at 298°K From the measured partial pressures, using estimated free energy functions, dissociation energies for Si2, Si3, SiC, SiC2, Si2C, Si2C2, Si2C3, and Si3C are calculated and compared with previously known dissociation energies for group IV B molecules

Thermodynamic study of SiC utilizing a mass spectrometer

Mass Spectrometric Study of Carbon Vapor

This report describes studies of photoionization and subsequent dissociation of all saturated paraffins from C2 to C6, plus n‐heptane and n‐octane, as a function of photon energy. The studies include data on all processes which occur below a photon energy of 11.9 ev. The instrument used was a mass spectrometer, combined with a Seya‐Namioka monochromator. The direct experimental data are presented as parent, fragment, and metastable ionization efficiency curves. For each molecule the family of curves obtained by dividing the derivatives of each normalized ionization efficiency curve by the derivative of the total ionization are presented. These derived curves facilitate the test of theories of dissociation kinetics.From a study of the total ionization curves, it is concluded that the adiabatic ionization transition is not accessible within the Franck‐Condon region and that it is therefore not possible to determine the ionization potentials of these molecules by ordinary impact experiments.The influence of ...

Photoionization of Alkanes. Dissociation of Excited Molecular Ions

Direct Determination of the Heat of Sublimation of Carbon with the Mass Spectrometer

The evaporation of alumina under nearly neutral conditions in tungsten and molybdenum Knudsen cells has been investigated by mass spectrometric methods. The atomization energies of the gaseous molecules are D0o(AlO) = 115±5 kcal/mole; D0o(Al2O) = 245±7 kcal/mole; D0o(Al2O2) = 365±7 kcal/mole.

Mark G. Inghram

Papers

Thermodynamic study of SiC utilizing a mass spectrometer

Mass Spectrometric Study of Carbon Vapor

Photoionization of Alkanes. Dissociation of Excited Molecular Ions

Direct Determination of the Heat of Sublimation of Carbon with the Mass Spectrometer

Thermodynamic Study of Al2O3 Using a Mass Spectrometer