Volume 21, Issue 9, 01 September 1953
Index of content:
21(1953); http://dx.doi.org/10.1063/1.1699273View Description Hide Description
An explanation is given of the extreme sharpness of the electron spin resonance line in solutions of potassium in liquid ammonia, as reported by Hutchison and Pastor. Motional narrowing of the width associated with dipolar and hyperfineinteractions results from the rotation and diffusion of ammonia molecules. The model of metal‐ammonia solutions used in the calculation is shown to be supported by thermal, magnetic, volumetric, and conductivity data. The model pictures the electrons removed from the potassium atoms as located in cavities in the liquid, the cavities having approximately the volume of two to four ammonia molecules. The electrons in the cavities are in equilibrium with respect to the reaction 2e⇆e 2+0.2 ev, where e 2 represents two electrons in a singlet state in one cavity. The electrons in cavities may perhaps be thought of as in molecular orbital states on the protons of the adjacent NH3 molecules.
On the Presence of Free Chlorine in Sodium Chloride Crystals Containing Color Centers and Color Center Precursors21(1953); http://dx.doi.org/10.1063/1.1699274View Description Hide Description
Measurements have been carried out of the free chlorine content of NaCl crystals subjected to electrolysis before and after exposure to x‐rays, as well as the free chlorine content of normal NaCl crystals after irradiation. It has been found that crystals which have not been irradiated contain no free chlorine, whereas those exposed to x‐rays contain between 0.1 and 0.6 free chlorine atom per vacancy pair.
The Interaction with Molecular Rotation of the Nuclear Electric Quadrupole Moments of Two Nuclei Having Spins 3/221(1953); http://dx.doi.org/10.1063/1.1699275View Description Hide Description
The theory of nuclear electric quadrupole effects in molecules is applied to the particular case of a molecule containing two nuclei each having spin 3/2. The matrix elements of the first‐order Hamiltonian of interaction between the nuclear electric quadrupole moments and the molecular rotational angular momentum are determined in the I 1 I 2 IJFMF representation. In one particular case the secular equations may be solved explicitly for the energy levels in terms of J, and the general solutions as well as their numerical values for J≤12 are given. For the other cases, higher‐order secular equations must be solved, and to facilitate this, coefficients in the expanded secular determinants have been computed. The method for obtaining relative line strengths for transitions is described, and numerical values of these are given for some transitions. Applications to the analysis of rotational spectra are also discussed.
21(1953); http://dx.doi.org/10.1063/1.1699276View Description Hide Description
The partial molal entropies for oxy‐anions and related species have been correlated as a function of the charge, interatomic distance, and certain structural factors. An equation is given by which the entropy for unknown species can now be estimated fairly accurately. In the few cases where the method does not give good agreement, the data are open to suspicion as indicated by other independent observations. Some applications and extensions of the method are indicated for future study.
21(1953); http://dx.doi.org/10.1063/1.1699277View Description Hide Description
A method is proposed by which the partial molal entropies of aqueous complex ions can be correlated in a simple manner as a function of the ratio of their charge to interatomic distance. The agreement obtained between the observed values and those calculated by this method has been shown to be within the accuracy of the experimental data. It is also demonstrated that when the complexing agent is water alone (i.e., no complexing) the proposed equation reduces to an expression similar to that previously obtained by Powell and Latimer for simple monatomic ions.
Empirical Considerations of Entropy. III. A Structural Approach to the Entropies of Aqueous Organic Solutes and Complex Ions21(1953); http://dx.doi.org/10.1063/1.1699278View Description Hide Description
A method for estimating the entropy of complex aqueous organic solutes and related species has been developed by a structural extension of a method of Powell and Latimer for simple solutes. The agreement between calculated and observed values is, in general, good, although systematic deviations begin to occur for very complicated and large solutes. The method is extended to the calculation of the entropies of charged organo‐metallic complex ions with good success, and possible applications to systems of biological interest are indicated.
Subsequent to the development of the general method for estimating the entropies of aqueous solutes, an empirical equation is also given for calculating gaseous entropies of both inorganic (ionic) and organic molecules from their structures.
21(1953); http://dx.doi.org/10.1063/1.1699279View Description Hide Description
The infrared absorption spectra of gaseous and liquid 1,4‐difluorobenzene have been obtained in the regions 2–22μ and 2–38μ, respectively, with the aid of LiF, NaCl, KBr, and KRS−5 prisms. The Raman spectrum of the liquid phase has been photographed with a three‐prism glass spectrograph of linear dispersion 15A/mm at 4358A. Depolarization ratios have been measured for the stronger Raman bands. A complete assignment of fundamental vibration frequencies has been made, and the spectra have been interpreted in detail. The nonplanar frequencies have been calculated with the aid of force constants determined for related molecules
21(1953); http://dx.doi.org/10.1063/1.1699280View Description Hide Description
The infrared absorption spectra of gaseous and liquid 1,2,4,5‐tetrafluorobenzene have been obtained in the region 2–22μ with the aid of LiF, NaCl, and KBr prisms. The Raman spectrum of the liquid phase has been photographed with a three‐prism glass spectrograph of linear dispersion 15 A/mm at 4358A. Relative intensities and depolarization ratios have been measured for the stronger Raman bands. A complete assignment of fundamental vibration frequencies is made and the spectra are interpreted in detail. The values of the nonplanar fundamental frequencies are checked by normal coordinate analysis.
21(1953); http://dx.doi.org/10.1063/1.1699281View Description Hide Description
The infrared absorptionspectrum of liquid 1,3‐difluorobenzene has been obtained in the region 2–22μ with the aid of LiF, NaCl, and KBr prisms. The contours of the strong infrared bands of the gaseous phase have also been observed in the region 5–22μ. The Raman spectrum of the liquid has been photographed with a three‐prism glass spectrograph of linear dispersion 15 A/mm at 4358A, and depolarization ratios have been measured for the stronger Raman bands. A complete assignment of fundamental vibration frequencies is given and the spectra are interpreted in detail.
21(1953); http://dx.doi.org/10.1063/1.1699282View Description Hide Description
The infrared absorption spectra of gaseous and liquid fluorobenzene have been obtained in the regions 2–22μ and 2–38μ, respectively, with the aid of LiF, NaCl, KBr, and KRS−5 prisms. The Raman spectrum of the liquid phase has been photographed with a three‐prism glass spectrograph of linear dispersion 15 A/mm at 4358A. A complete assignment of fundamental vibration frequencies is given, and the spectra are interpreted in detail.
21(1953); http://dx.doi.org/10.1063/1.1699283View Description Hide Description
Some generalizations of previous theoretical expressions for the mean potential energy of interaction between two randomly disordered molecules have been derived and have been generalized to interactions in a molecular lattice. Values of the heats of vaporization of some tetrahedral molecules and halogens have been calculated, with results in reasonable agreement with experimental values. Application of the theory to the heat of sublimation of a disordered solid, hexachloroethane, is also discussed.
21(1953); http://dx.doi.org/10.1063/1.1699284View Description Hide Description
The paper outlines the principal characteristics of the effects of irradiation on the discharge current in an ozonizer. The ``electronic surface charge theory'' of the effect developed by Deb and Ghosh, on a suggestion of Mitra, is explained and is further extended by taking into account the role played by the negative ions formed in the discharge space. It is assumed that the effect of irradiation is to decrease the charges deposited on the surface and to increase those in the volume. The former reduces the discharge current due to the neutralization of the surfacecharges and the latter increases the main discharge current due to the applied voltage. The net effect is generally a decrease if conditions are favorable for the capture of the electrons in the volume by neutral gas molecules, leading to the formation of negative ions. In all other conditions the effect is generally an increase. It is shown that the theory, in its extended form, is able to account for the origin and the characteristics of both the positive and the negative effects. Numerical calculations of the various rate processes involved in the proposed mechanism are also made. It is shown that the relative magnitudes of these processes are such as to support strongly the ``electronic surface charge theory'' of the effect.
21(1953); http://dx.doi.org/10.1063/1.1699285View Description Hide Description
Simple carbon systems have been irradiated with the University of Chicago betatron, producing C11 atoms by the reaction C12(γ,n)C11. The distribution of the radioactive atoms between CO and CO2 for samples irradiated in the liquid phase was found to be 95–100 percent CO, and for samples irradiated in the solid phase about 50 percent of each oxide. A mechanism for these results is proposed.
Hot Atom Chemistry of the Alkyl Bromides; Absence of Effects Due to High Radiation Density; Isotope Separation in Solids21(1953); http://dx.doi.org/10.1063/1.1699286View Description Hide Description
A 30‐curie polonium‐beryllium neutron source which gives less than 0.1 roentgen per hour in close contact was used to study the hot atom chemistry of a selection of alkyl bromides. Comparison of the results with those obtained with ordinary neutron sources containing gamma rays in abundance up to 700 roentgen/hour equivalent strongly indicates that the essential phenomena reported are free of effects due to the gamma‐radiation density.
The separation of the bromine isotopes in crystalline alkyl bromides has been observed in several additional cases. No isotope effect is shown with CBr4, however, nor with frozen glasses. The possible theoretical significance of these results is discussed.
21(1953); http://dx.doi.org/10.1063/1.1699287View Description Hide Description
Experimental evidence is presented for the DCl+1, HCl+1, DCl+2, and HBr+2 molecular ions, using a modified Consolidated‐Nier mass spectrometer. Although Cl+3, Br+3, and A+3 were observed, no evidence was obtained for H1,2Cl+Z , or HBr+Z above Z=2. This result contradicts the recent calculations of Magee and Gurnee2 that HBr+3 and HBr+4 would be stable toward dissociation. Finally a crude calculation is done assuming hydrogen 1s atomic orbitals which agrees amusingly with the experiments.
21(1953); http://dx.doi.org/10.1063/1.1699288View Description Hide Description
Quantitative measurements of apparent rotational line half‐widths are described for NO, HCl, and HBr. Theoretical relations, which apply to vibration‐rotation bands with spectral lines of uniform half‐width and Lorentz contour, have been used to obtain apparent rotational half‐widths from experimental data for CO and for NO.
21(1953); http://dx.doi.org/10.1063/1.1699289View Description Hide Description
The appearance potentials of the vinyl ion as produced by electron impact from eight different compounds have been measured. The corresponding values of the heat of formation of the vinyl ion vary from 274 to 292 kcal/mole, with an average value of 281.5 kcal/mole. It is pointed out that no definitive explanation for the variation can be given.
The heat of formation of the vinyl radical is found to be 82.3 kcal/mole, which leads to a value of 122 kcal/mole for the first C–H bond dissociation energy in ethylene. The ionization potential of the vinyl radical is 200.5 kcal/mole=8.69 ev.
21(1953); http://dx.doi.org/10.1063/1.1699290View Description Hide Description
The increasing use of infrared dichroism measurements in studying the molecular structure of fibrous proteins necessitates a critical examination of its interpretation. Relationships between transition moment direction and dichroic ratio are derived for perfectly and imperfectly oriented fibers, and the effects of reflection losses, form dichroism, and convergence are considered. Uncertainties in the assignment of the transition moment directions associated with the principal vibrations of the —CO·NH— group are discussed.
21(1953); http://dx.doi.org/10.1063/1.1699291View Description Hide Description
The absolute intensities of the fundamental infrared absorption bands of SiF4, CF4, and SF6 were measured utilizing the pressure broadening technique. The effective bond moments, μ0, and bond moment derivatives, ∂u/∂r, are calculated as a function of the most general potential constants. Based on a valence force field plus repulsion between nonbonded atoms, the most probable values (first column) and the alternatives (second column) are as follows:The results are discussed.
21(1953); http://dx.doi.org/10.1063/1.1699292View Description Hide Description
When chemisorption on a semiconductive solid is accompanied by electronic charge transfer between adsorbate and solid, an electronic boundary layer analogous to that in rectifying junctions may develop and polarization of charges in the solid may result. These phenomena may limit or control the chemisorption characteristics. The boundary layer theory developed for electrical contacts and elementary considerations concerning the effect of the polarization potential are applied to derive the form of relationships for the extent, heats, and rates of chemisorption and some consequences with respect to catalysis. An attempt is made to illustrate the detailed physical processes in order to examine the meaning of ``heterogeneity'' and ``active centers'' in cases of this type of chemisorption.