Volume 22, Issue 12, 01 December 1954
Index of content:
22(1954); http://dx.doi.org/10.1063/1.1739974View Description Hide Description
A set of force constants for F2CO has been calculated using the observed fundamental frequencies and a potential function consisting of valence force interaction terms and an additional term involving an interaction between the oxygen and fluorine atoms. The large values obtained for the interaction constant and the angle deformation constants were related to interaction forces between the terminal atoms.
Also included in this paper are calculations of the thermodynamic properties of F2CO and FClCO.
22(1954); http://dx.doi.org/10.1063/1.1739975View Description Hide Description
The electrical effects accompanying the steady fall of solid charged spherical particles under gravity in an electrolyte are examined theoretically. For a single particle falling in an infinite electrolyte, it is shown that, owing to fluid flow round the particle, the double layer field is modified. The effect in the double layer region is complicated, but outside this region a field is set up of the same form as that which would arise from a dipole fixed at the center of the particle with its axis vertical. A general expression is given for this dipole field in the case of nonconducting particles. The calculations extend previous work in that no restriction on the relative dimensions of the particle size and the double‐layer thickness is imposed.
It is shown that the interaction between the charge on the particle and the modified field alters the sedimentationvelocity of the particle. The calculations show that in practical cases the effect might, in favorable circumstances, reduce the velocity by a few percent.
The analysis is extended to suspensions containing a large number of particles uniformly distributed.
22(1954); http://dx.doi.org/10.1063/1.1739976View Description Hide Description
Consistency theorems are derived from the general Lindemann theory of unimolecular reaction rates; one can make several general statements about the signs of the slopes and curvatures of plots of observed rate constants against a function of the pressure. Observed rate constants and simple combinations of observed rate constants are interpreted in terms of Tolman's distribution function, the distribution of molecules which react. Moments of the ratio of rate constant for decomposition to that for deactivation by collision, ci/bi , can be found at any pressure. By means of Schwarz's inequality one can find several dimensionless quantities which provide consistency tests with respect to the statistical interpretations and which provide a check against a wrong assignment of the high‐ or low‐pressure limit. These methods are used to examine the data for cyclobutane, cyclopropane, nitrogen pentoxide, and nitrous oxide. Previous interpretations given to the data on the last two cases are revised. The average detailed rate constants for molecules which react are estimated using an approximate relation.
22(1954); http://dx.doi.org/10.1063/1.1739977View Description Hide Description
The quadrupole coupling constant and dipole moment of the CH3Cl molecule have been investigated as functions of the hybridization and ionic character. It is found that somewhat different results are obtained if one includes the effect of overlap in calculating the quadrupole coupling constant. The inclusion of overlap is contrary to the usual assumption that the quadrupole coupling constant arising from a purely covalent chlorine pbond is the same as the quadrupole coupling constant of a free chlorine atom. The results suggest that more s hybridization of the chlorine bonding wave function occurs than is assumed by Townes and Dailey and there is some indication of the occurrence of an appreciable amount of 3d character in this function. No precise assignment of values for the ionic character and hybridization appeared feasible.
22(1954); http://dx.doi.org/10.1063/1.1739978View Description Hide Description
Morphological and structural details of siliconcarbide type 141R are given. This polymorph, having a structure represented by the zigzag sequence 3333333333333332, is a member of the `3...2' rhombohedral series proposed by Ramsdell [Am. Mineralogist 32, 64 (1947)].
A detailed study of the `3...2' series is undertaken, resulting in an empirical mechanism which can be used for the direct determination of the structure of any member of this series. Using this means the structure of the new polymorph 393R is suggested.
22(1954); http://dx.doi.org/10.1063/1.1739979View Description Hide Description
A method has been devised to prepare CF2 = CD2 and CF2 = CHD. The infrared spectra of the gaseous compounds and the Raman spectra of the liquids have been determined. The observed frequencies have been assigned to the fundamental modes of vibration and to overtones and combinations. The torsional frequency has been estimated as ca 720 and ca 520 cm—1 in CF2 = CH2 and CF2 = CD2, respectively. The overtone of the torsional frequency interacts with the CH2 or the CD2 deformation fundamental and this is the cause of the anomalous results with the product rule.
Effect of Intermolecular Interactions between CH Frequencies on the Infrared Spectra of N‐Paraffins and Polythene22(1954); http://dx.doi.org/10.1063/1.1739980View Description Hide Description
A systematic study has been made of the infrared absorption band near 725 cm—1 which arises from the rocking vibration of methylene groups in n‐paraffins and in polyethylene. In unoriented crystals of n‐paraffins, this band exhibits two components of equal intensity below the transition point; above the transition temperature and in the liquid state only the higher frequency component is found. In solid cold‐drawn polyethylene the two components are of unequal intensity, the low frequency component being the stronger; in liquid polyethylene only the lower frequency component is found. Studies were made of polyethylene in various states of crystallinity and orientation, using both polarized and unpolarized radiation. The results obtained can be consistently interpreted, if the higher frequency component is attributed to crystallites in the polyethylene and the lower frequency component is assumed to be due partly to the crystalline and partly to the amorphous form of the polyethylene. It is concluded that the doubling of this frequency arises from some interaction between methylene groups which is peculiar to the crystalline state of long chain n‐paraffins below their transition points.
22(1954); http://dx.doi.org/10.1063/1.1739981View Description Hide Description
An investigation of the infrared spectrum of gaseous NO2Cl and the Raman spectrum of liquid NO2Cl results in the following assignment of fundamental frequencies: The structural implications of the data are discussed, and it is concluded that the structure is .However, it is not possible to say whether the molecule is planar or pyramidal.
22(1954); http://dx.doi.org/10.1063/1.1739982View Description Hide Description
The work reported here is an application of free precession or ``spin echo'' techniques in nuclear magnetic resonance to a study of the properties of liquids under high pressure. The proton relaxation timeT 1 was measured as a function of pressure, over the range 1 to 10 000 atmospheres, for six liquids:water,n‐pentane, n‐hexane, toluene, ethyl iodide, and methyl iodide. In addition to the relaxation time, the normalized values D(P)/D(1) of the self‐diffusion constant were measured as a function of pressure for water and methyl iodide.
In each liquidT 1 decreases with increasing pressure. However, comparison of the observed variation of T 1 with pressure with Bridgman's data on the variation of viscosity η with pressure shows in all cases (except that of methyl iodide for which no viscosity data are available) that T 1 is not simply proportional to 1/η, but instead T 1η increases with pressure. Similarly, for water and methyl iodide, the diffusion constant D varies in such a way that T 1/D increases with pressure. For water the Stokes‐Einstein relation Dη = cT is obeyed within the errors of observation. The behavior of T 1 can be understood if one assumes that the dominant relaxation mechanism involves intramolecular fields, whose correlation time is determined by the rotational freedom of the molecule, and that compression of the liquid inhibits migrational freedom more drastically than rotational freedom.
The necessity of making the present measurements has led to the discovery that BeCu, a heat treatable alloy, makes a very satisfactory high pressure, non‐magnetic bomb which might well be used for other magnetic investigations under high pressure.
22(1954); http://dx.doi.org/10.1063/1.1739983View Description Hide Description
2‐, 3‐, and 4‐mono‐deutero‐pyridine have been prepared and the microwave spectra recorded. For each of the isotopic species 11—12 transitions (Q‐ and R‐branch lines) were localized, a number of which could be identified by their Stark effect. For all three species rotational constants of high precision were calculated. The material so provided in connection with known rotational constants for ordinary pyridine is insufficient for a complete determination of the ten geometrical parameters of the molecule. Seven models with a choice of C – H distances close to the correct value (1.075‐1.085 A) were considered one of which was shown to be consistent with electron‐diffraction work and current valence theory. In this model d(N – C(2)) = 1.340±0.005; d(C(2) – C(3)) = 1.390±0.005; d(C(3) – C(4)) = 1.400±0.005 A. The valence angles in the aromatic ring (starting with the C(6) – N – C(2) angle) are: 116° 42′; 124° 00′; 118° 36′; 118° 06′.
22(1954); http://dx.doi.org/10.1063/1.1739984View Description Hide Description
Vibrational relaxation times at temperatures between 400°K and 1500°K have been measured in chlorine and carbon dioxide with a shock tube. The approach toward equilibrium vibrational excitation behind the shock wave is obtained from the density profile of the transition region using an optical interferometer. The measurements were made with a relatively narrow shock tube in order to avoid errors caused by optical distortions. The accuracies of the measuredrelaxation times are estimated to be from 20 percent to 50 percent.
22(1954); http://dx.doi.org/10.1063/1.1739985View Description Hide Description
The pure nuclear quadrupole resonance frequencies of the Br79isotope are given for a number of previously unreported bromobenzene derivatives. The resonance frequencies of the Br81isotope in these and other previously reported compounds are compared with the electron density in the vicinity of the carbon atom to which the bromine is bonded.
22(1954); http://dx.doi.org/10.1063/1.1739986View Description Hide Description
The organic retentions for (d,p), (n,2n), and (γ,n) activation of iodine in liquid methyl and ethyl iodide, containing added iodine, have been found to be equal to the retentions observed in radiative neutron capture. This demonstrates that the chemical effects are independent of the recoil energy of the activated nucleus, of the mode of nuclear formation, and of variation of fragmentation effects within the recoil track. In the absence of scavenger iodine, the increase in retention due to radiation damage is less than 10 percent in all cases studied.
22(1954); http://dx.doi.org/10.1063/1.1739987View Description Hide Description
The infrared spectrum of C2D2 has been reinvestigated in the region 500 to 8000 K with a prism‐grating spectrometer. Thirty‐nine absorption bands were observed, of which twenty‐six are new, and ten have been resolved into rotational fine structure. This brings the present total of observed bands to fifty one. Figures of the bands are shown, wave numbers of all observed lines are given in kaysers reduced to vacuum, and the absorption regions are described. All the bands observed have been given vibrational assignments, and a vibrational analysis has been made which yields the wave numbers of the harmonic frequencies and the values of the anharmonic constants. Rotational analyses of all the resolved bands have been made, and from these the rotational constants which agree with those obtained by Saksena have been determined.
22(1954); http://dx.doi.org/10.1063/1.1739988View Description Hide Description
The spectrum of 1,1‐difluoroethane has been investigated over the region 18 000 Mc to 38 000 Mc with a conventional Stark‐modulation spectrometer. This molecule is a moderately asymmetric rotor of the oblate type with components of its dipole moment along the A and C axes. About 30 lines have been identified with the aid of the Stark effect and an approximate model for the molecule. The analysis yields the following rotational constants:A=9491.95 Mc; B=8962.65 Mc; C=5170.43 Mc; x=0.75504. The barrier hindering internal rotation has been determined as (1.25±0.20)×103 cm—1 from intensity ratio measurements of the torsional frequency.
22(1954); http://dx.doi.org/10.1063/1.1739989View Description Hide Description
The emission bands of the NO molecule excited in an impure afterglow were studied in the vacuum ultraviolet region. The abrupt cutoff at a certain ν′ value was observed in the β, γ, and δ bands and also the non‐appearance of the ε, and β′ bands was confirmed. An explanation for these observations was attempted in connection with the dissociation energy of the NO molecule and with the mechanism of the afterglow.
22(1954); http://dx.doi.org/10.1063/1.1739990View Description Hide Description
The crystal structure of lithium sulfate monohydrate has been reinvestigated in order to determine the position of the hydrogen bonds and to check on the asymmetry of the sulfate group in this substance suggested by the earlier work of Zeigler.
A disposition of the hydrogen bonds in agreement with the protonmagnetic resonance results has been found and the sulfate group has the configuration of a regular tetrahedron within the limits of error of our measurements. Our results are in agreement with Zeigler in most essentials.
22(1954); http://dx.doi.org/10.1063/1.1739991View Description Hide Description
A procedure is developed for the machine computation of the partition functions for non‐rigid rotating anharmonic oscillators. Vibrational‐rotational coupling terms and low temperature rotational corrections are included. A general code has been designed to permit the calculation of the ideal gas thermodynamic functions for a large variety of molecular structures on the National Bureau of Standards Eastern Automatic Computer—SEAC. The method is illustrated by evaluating the thermodynamic functions for an asymmetric top molecule. Tables of Cp 0/R, (H 0–E 0 0)/RT, (E 0 0–F 0)/RT, and S 0/R have been evaluated for H2O, HDO, D2O, HTO, DTO, and T2O at close intervals from 50° to 5000°K. The time required for these computations is of the order of several minutes per molecule. The results for H2O are in good agreement with those obtained by direct summation.
Study of Carbon Monoxide, Nitrogen, Propylene, and Benzene Ionization Probability Curves near Threshold22(1954); http://dx.doi.org/10.1063/1.1739992View Description Hide Description
Ionization probability curves for the formation of CO+, N2 +, C3H6 +, and C6H6 + have been obtained for some six volts above threshold. The technique employed provided both ionization by essentially monoenergetic electrons and a m/ε separation of the ions. In the case of the diatomic ions, the structure in the curves can be interpreted in terms of spectroscopically identified energy levels. The curves for propylene and benzene exhibit considerable structure which, when analyzed in a similar manner to that used for the diatomic molecules, results in the location of a number of unidentified energy levels. The presence of these levels explains the discrepancies in ionization potential measurements obtained by various electron impact methods.
22(1954); http://dx.doi.org/10.1063/1.1739993View Description Hide Description
Magnetic susceptibilities of Na2IrCl6, Na3IrCl6·2H2O, and (NH4)2Ir(H2O)Cl5 were determined for these solids and for aqueous solutions 0.6f in the complex compound and 1f in HCl by the Gouy method. Na2IrCl6 is paramagnetic in the solid state and in solution, with a magnetic moment corresponding to one unpaired 5d electron and to d 2 sp 3 covalent Ir–Cl bonds. The two iridium (III) complexes are diamagnetic, corresponding likewise to d 2 sp 3bond formation.