Absolute Energy Levels Research Articles

Electrode behaviour of insoluble suspensions of metal-free phthalocyanines in methylene chloride

A new method of investigating photoactive pigment particles, based on electrochemical measurements on suspended particles in a dielectric fluid containing an indifferent electrolyte is discussed. This technique provides information on the absolute valence and conduction energy levels and band gaps of organic pigments as well as the distribution of states in these solids. The voltammetric oxidations and reductions of theα,β andx-forms of metal-free phthalocyanine (H2Pc) suspended in methylene chloride were examined on the surface of a hanging mercury drop electrode (HMDE) and a Pt disc electrode (PDE). One of the more significant aspects of the electrochemical studies of these suspensions is that substances of identical chemical composition but different solid state structure, such asα,β andx-H2Pc, could be examined under the same experimental conditions to give detailed electrochemical information which could be related to the valence and conduction levels.

Determination of the absolute energy levels of organic molecules in the gas phase and in condensed media. I. Solution and gas phase ionization energies and electron affinities of substituted pyridine-N-oxides

The basic principle for the determination and interrelation of the absolute energy levels of organic molecules in the gas phase and condensed media are discussed. The electrochemical and gas phase data for a series of substituted pyridine-N-oxides were used to examine the validity of Born’s formula, which approximate the chemical solvation energies of ions. A linear free-energy relationship between the gas phase ionization potentials (I.P.) and the electrochemical half-wave oxidation potentials (Eox1/2) for substituted pyridine-N-oxides was found. This relationship was utilized to predict the ionization potentials of other heterocyclic amine-N-oxides whose I.P.’s have not been measured. The estimated effective ionic radius reff for pyridine-N-oxide derivatives was found to be highly dependent on the nature of the substituent and linearly related to the electrophilic substituent constant σ+. Substituted pyridine-N-oxides have moderately low ionization energies and form stable positive radical cations. Their use as hole traps when immersed in insulating fluid in contact with photoconductors will be discussed.

SEISMIC SIGNATURES OF LARGE AIR GUNS

Large chamber air guns are a reliable and effective source of energy for marine seismic surveys. Air guns with chamber volumes of 300 and 1000 cubic inches demonstrate desirable low‐frequency responses and high absolute energy levels. Overall performance has been compromised, however, by the bubble effect. Previous attempts at minimizing the bubble response have resulted in loss of reliability, reduced power, or incomplete bubble suppression, or a combination thereof. In this paper, we present the results of experimental tests on air guns with 300 and 1000 cubic inch chambers and describe a divided‐chamber gun which greatly attenuates the bubble effect. Significant improvements in the width and flatness of the frequency spectra are demonstrated by analysis of the actual signatures obtained in deep water and with record sections comparing the results obtained with the standard and improved guns along an identical traverse. The bubble‐attenuating air gun simultaneously provides improved resolution, high absolute‐energy levels, and excellent reliability.

Localized impurity states in the Hartree‐Fock, LCAO approximation II. The F Center in KCI

AbstractWe apply the techniques of a previous paper (I) to the F center in KCl. Our purpose is to place the application of Hartree‐Fock methods to the F center on a firm theoretical basis by calculating in a consistent manner the magnitude and effect of approximations commonly made in less complete treatments. It is shown that the familiar point‐ion approximations and crystal‐field approximations with partial consideration of exchange effects are special cases of our results. We compute wave functions and energies step by step for each of the various levels of approximation possible with our model. It is found that the functions resulting from the point‐ion model are not good approximations to the final wave functions. Our results show that exchange effects with at least the first two shells of nearest neighbors should be considered since they are of the same order of magnitude as terms in the point‐ion model. Overlaps of the F‐center function with ion functions out to sixth neighbors are considered. The absorption energy for the F center is calculated to be 0.1619 Ry as compared with the experimentally observed energy of 0.170 Ry. The magnetic hyperfine structure contact terms are calculated for the first two shells of nearest neighbor ions, using approximate orthogonalized functions, and found to be 29.7 Mc/h for the nearest neighbor K+ ions and 10.9 Mc/h for the next nearest neighbor Cl− ions. The experimentally observed values are 21.6 and 7.0, respectively. Given these differences and the excessively low values of the one‐electron energies, it is concluded that electronic and ionic polarization effects in the ionized crystal states must be considered to calculate accurate F‐center wave functions and absolute energy levels.

Reevaluation of X-Ray Atomic Energy Levels

All of the x-ray emission wavelengths have recently been reevaluated and placed on a consistent \AA{}* scale. For most elements these data give a highly overdetermined set of equations for energy level differences, which have been solved by least-squares adjustment for each case. This procedure makes "best" use of all x-ray wavelength data, and also permits calculation of the probable error for each energy difference. Photoelectron measurements of absolute energy levels are more precise than x-ray absorption edge data. These have been used to establish the absolute scale for eighty-one elements and, in many cases, to provide additional energy level difference data. The x-ray absorption wavelengths were used for eight elements and ionization measurements for two; the remaining five were interpolated by a Moseley diagram involving the output values of energy levels from adjacent elements. Probable errors are listed on an absolute energy basis. In the original source of the present data, a table of energy levels in Rydberg units is given. Difference tables in volts, Rydbergs, and milli-\AA{}* wavelength units, with the respective probable errors, are also included there.