Index of content:
Volume 25, Issue 4, 01 October 1956
25(1956); http://dx.doi.org/10.1063/1.1743009View Description Hide Description
The liquid structuretheory of Born and Green is used to interpret x‐ray diffraction measurements on liquid sodium and potassium to find an effective interatomic potential function for pairs of sodium and pairs of potassium atoms. This potential function predicts approximately the correct binding energy for solid sodium and potassium, and when reinserted in the x‐ray formulas predicts scattering curves at higher temperatures which are in good agreement with experiments.
25(1956); http://dx.doi.org/10.1063/1.1743010View Description Hide Description
The Born‐Green theory of liquids is extended to the case of liquid mixtures, and a formula for the x‐ray scattering by such liquids is developed. The formula is used to calculate the x‐ray scattering by a liquid sodium‐potassium alloy, and fair agreement with the experimental scattering is found.
25(1956); http://dx.doi.org/10.1063/1.1743011View Description Hide Description
The effect of crystal field symmetry on the appearance of K x‐ray absorption edges of metal ions in complexes is considered. In particular, the splitting of the 1s—4p absorption for first row transition elements is related to the splitting of the degeneracy of the 4penergy levels in the ion by the crystal field.
25(1956); http://dx.doi.org/10.1063/1.1743012View Description Hide Description
It is shown that the crystal field splitting of the 4p orbitals of Cu(II) in some complexes can be correlated with the splitting of the 1s—4p transition observed in studies of the K absorption edges of these complexes, provided the ligand‐metal bonding is not appreciably covalent.
25(1956); http://dx.doi.org/10.1063/1.1743013View Description Hide Description
Measurements have been made of the scattering of xenon atoms with energies between 700 and 2100 ev in room temperature xenon. The interaction potential for two xenon atoms, deduced from the variation of total collision cross sections with energy, may be expressed asfor r between 3.01 A and 3.60 A. This potential is consistent with others, valid at larger separation distances, which have been obtained from measurements of gaseous compressibility, transport, and crystal properties, within the limits of uncertainty of the potentials at the larger distances.
25(1956); http://dx.doi.org/10.1063/1.1743014View Description Hide Description
The potential energy of interaction between a hydrogen atom and a helium atom has been calculated as a function of separation distance by standard quantum mechanical variation procedures. The approximate molecular wave functions used contained both homopolar and ionic contributions, and were constructed from 1s hydrogen‐like atomic wave functions. All integrals involved have been evaluated accurately. The results are in agreement with a potential determined from measurements of the scattering of high velocity hydrogen atoms in helium gas. For separation distances greater than 1 A, the results have been combined with an estimate of the potential of the London dispersion forces, and the combination has been represented by an exp‐six potential useful in the calculation of properties of gases.
25(1956); http://dx.doi.org/10.1063/1.1743015View Description Hide Description
Total collision cross sections have been measured for hydrogen atoms with energies between 700 and 2100 ev, scattered in room temperature helium. The results have been analyzed to obtain potential energy information for the interaction between a hydrogen atom and a helium atom. The potential function, which may be represented byfor r between 1.16 A and 1.71 A, gives values which agree with those calculated quantum mechanically by Mason, Ross, and Schatz.
The H–He potential has been combined with a potential previously obtained for He–He to obtain a function which, it is suggested, represents the repulsive interaction between two hydrogen atoms. The derived function is in fair agreement with theoretical calculations of Hirschfelder and Linnett for the repulsive 3Σ state of the hydrogen molecule.
25(1956); http://dx.doi.org/10.1063/1.1743016View Description Hide Description
Total collision cross sections have been measured for neon atoms with energies between 500 and 2100 ev, scattered in room temperature argon, and for argon atoms with the same energies scattered in room‐temperature neon. The experimental results have been analyzed to obtain the following potential energy of interaction between a neon atom and an argon atom:for r between 1.91 A and 2.44 A.
This potential is in agreement with one obtained by a simple combination of the potential between two neon atoms with that between two argon atoms. It is also consistent with the potential, valid at larger separation distances, which has been derived from measurements of gaseous compressibility, viscosity, and crystal properties.
25(1956); http://dx.doi.org/10.1063/1.1743017View Description Hide Description
Direct evidence is presented to show that whiskergrowth by vapor deposition occurs at the tip rather than the base. Platelets are shown to grow at constant thickness by the action of a set of crossed‐screw dislocations, and whiskers are shown to bear no screw dislocations normal to their axis.
25(1956); http://dx.doi.org/10.1063/1.1743018View Description Hide Description
A mechanism for the vapor deposition of mercury platelets is presented. The growth behavior is accounted for on the basis of a single screw dislocation in a  crystallographic direction. The growth of whiskersversus platelets is determined by preferential nucleation of (100) or (110) planes on the active sites.
25(1956); http://dx.doi.org/10.1063/1.1743019View Description Hide Description
Electron attachment leading to the formation of SF6 — and SF5 — in sulfur hexafluoride has been investigated using nearly‐monoenergetic electrons of established energies of less than 2 ev. The dissociative attachment process leading to the formation of SF5 — maximizes at less than 0.1 ev and then decreases to zero at approximately 1.5 ev. In the case of resonance capture leading to the formation of SF6 —, the capture process occurs at less than 0.1 ev and only over an energy range estimated to be not larger than 0.05 ev. This leads to an estimated cross section for this resonance capture process of 10—15 cm2. A discussion is given of the method used in the establishment of the electron energy scale at such low energies and the use of the resonance capture process for measuring electron energy distributions.
25(1956); http://dx.doi.org/10.1063/1.1743020View Description Hide Description
The effective distribution coefficient of boron in germanium has been measured as a function of crystal growth rate. Its behavior is shown to agree with that predicted by the theory of Burton et al. for a solute whose equilibrium distribution coefficient is greater than unity. The coefficient decreases rapidly with increasing growth rate from its equilibrium value 17.4 to 2.2 at a growth rate of 10—2 cm/sec.
25(1956); http://dx.doi.org/10.1063/1.1743021View Description Hide Description
The solubility of lithium in silicon from a lithium‐silicon alloy phase has been redetermined. The original data of Fuller and Ditzenberger appear to be in error. The solubility of lithium, from the same phase, in boron‐doped silicon has also been determined. At both low and high temperatures the solubility in the doped crystal markedly exceeds that in the undoped one. In fact, the solubility just about equals the boron concentration in these ranges. The low temperature disparity can be explained in terms of hole‐electron equilibria while the high temperature effect is believed due to covalent bond formation between lithium and boron. A quantitative theory is developed which predicts the experimental results.
25(1956); http://dx.doi.org/10.1063/1.1743022View Description Hide Description
The infrared spectrum of methyl isocyanide vapor has been remeasured with medium resolving power from 1.7–10μ and in the far infrared region around 38μ. From these observations it has been possible to obtain unequivocally the three degenerate fundamental vibration frequencies v 6, v 7, and v 8, and the symmetric frequency v 3. Thermodynamic properties are calculated for the molecule. In addition the spectrum of acetonitrile vapor has been remeasured abound 6μ with slightly increased resolving power and the v 3 and v 6 fundamental frequencies obtained.
25(1956); http://dx.doi.org/10.1063/1.1743023View Description Hide Description
General formulas for kinetic energy matrix elements are given in terms of internal coordinates of the bond stretching and bending type for in‐plane vibration in planar molecules. The definition for the sign of bond angle makes those formulas independent of the mutual positions of atoms. An example is given.
25(1956); http://dx.doi.org/10.1063/1.1743024View Description Hide Description
The relation between the radius of the Gibbs dividing surface and the superficial density is investigated in detail and the generalized Kelvin relation is obtained. Consequently the fundamental equation for spherical interface is expressed by . The generalized Kelvin relation is the explicit differential equation for determining the location of the surface of tension which does not contradict with the conventional one. Thus the mathematical formalism of thermodynamics will be completed for treating spherical interface in a rigorous and self‐consistent manner, the last ambiguous point being eliminated from the conventional Gibbs treatments.
25(1956); http://dx.doi.org/10.1063/1.1743025View Description Hide Description
Two features of aqueous polyethylene glycol solutions (molecular weights 285 to 6600) have been noted in experiments with silver membrane osmometers: first, the solutions can be forced through the membranes in a manner which is indicative of capillary viscousflow; second, the osmotic pressures of polyethylene glycols are such that the limits of the reduced osmotic pressure as the concentration tends towards zero are of the form KM α, when K and α are positive numbers, instead of RT/M as is indicated by thermodynamictheory. The differences between theoretical and observed osmotic pressures are interpreted as being due to diffusion of solute through the membranes. On this basis diffusion coefficients are calculated for the diffusion of polyethylene glycol through the membranes. For an estimated molecular weight of 400 000 the membranes are semipermeable. Similar work has been done on polystyrenes (molecular weights 180 000 to 673 000) and the membrane are shown to be semipermeable for polystyrenes of molecular weights greater than 500 000.
25(1956); http://dx.doi.org/10.1063/1.1743026View Description Hide Description
Dissociative recombination of NO+ ions with electrons was shown to take place when NO is irradiated with krypton resonance radiation at 1236 A. Application of a dc voltage across the reaction cell produces an increased rate of decomposition by electron or positive ion bombardment of neutral NO molecules.
25(1956); http://dx.doi.org/10.1063/1.1743027View Description Hide Description
Experiments have been carried out to determine whether nonthermal rotational distributions in the 2Σ+ electronic state of OH observed in certain flames are caused by self‐absorption. A study of emission (single and double path) and absorption by OH between 3064 A and 3350 A in atmospheric and low‐pressure flames has shown that self‐absorption is negligible in at least two cases in which nonthermal distributions are found. This leads to the conclusion that anomalous ``temperatures'' of OH measured previously in hydrocarbon flames at low pressure and in highly diluted flames at atmospheric pressure are real.
25(1956); http://dx.doi.org/10.1063/1.1743028View Description Hide Description
This paper contains an effective mass‐quantum mechanical investigation of the ionizability of interstitial hydrogen and lithium in germanium and silicon. It is concluded that hydrogen should not ionize while lithium should. This seems in accord with experimental findings.