Key words: mathematical modeling, network; network, tensile properties; paper, interfiber bonding; paper, low-density handsheets; paper, pulp characterization; paper, `tensile testing.

The tensile behavior of a thin web-like paper network was simulated by two simple mathematical models. The mesh distortion, drop in tensile force and energy loss resulting from breakage of a network junction were calculated. These results were used to formulate two parameters for characterizing interfiber adhesion: a parameter averaging the network energy losses incurred in a series of bond breaks when the network is elongated and a parameter averaging the force drops. The effect of mesh size, local bond adhesive force, and size and shape of the specimen network were calculated. These results based on model studies were used to interpret behavior observed in an actual paper network.

A class of double integrals involving Gaussian and trigonometric factors, D. M. Fradkin, J. Res. Nat. Bur. Stand. (U.S.), 84, No. 4, 319-326 (July-Aug. 1979).

Key words: definite integrals; double integrals; error functions; Fourier transforms; radiation reaction.

The five parameter double integral S。 dy exp(−p3y3) sin(ẞy + ) times ƒ 。 dx exp(−x2) cos(eßx + ) is evaluated in terms of Fourier transforms of exp(−x2)erfc(ax). Some new expressions for these transforms are obtained.

September-October 1979

A high precision load cell mass comparator, R. M. Schoonover, J. Res. Nat. Bur. Stand. (U.S.), 84, No. 5, 347-351 (Sept.Oct. 1979).

Key words: constant loading; force; high precision; highprecision weighing; load cell; mass; mass comparator; mass difference; strain-gage; substitution weighing; weighing; weights.

Described here is a simple mechanical method used to fabricate a high precision mass comparator using a bonded strain gage load cell. Results indicate that a standard deviation of less than 0.0003% is readily attainable, and the device works well for objects normally considered too unwieldy for large high-precision balances.

Molecular interpretations of modulus and swelling relations in natural rubber cross-linked by dicumyl peroxide, L. A. Wood, J. Res. Nat. Bur. Stand. (U.S.), 84, No. 5, 353-358 (Sept.Oct. 1979).

Key words: cross-linking of rubber; dicumyl peroxide; elasticity theory of rubber; modulus of rubber; MooneyRivlin constants; rubber elasticity theory; rubber, natural; swelling of rubber network.

A survey of published experimental work on the modulus of natural rubber cross-linked by dicumyl peroxide permits a comparison with the results and molecular interpretations obtained in recent NBS work [J. Res. NBS 76A, No. 1, 51 (1972), 77A, No. 1, 171 (1973) and 80A, No. 3, 451 (1976)]. Excellent agreement was found among values of the shear modulus G at the same cross-linking when the cross-linking is calculated from the amount of decomposed dicumyl peroxide. The types of deformation included torsion as well as uniaxial extension and compression. G increases linearly with cross-linking (except at the lowest degrees) with a slope from 5 to 15 percent greater than that predicted by the simple statistical theory. Data of Mullins demonstrated that at each degree of cross-linking the value of G is intermediate between 2C, and 2(C1 + C2) where

C1 and C2 are the Mooney-Rivlin constants. Measurements of equilibrium swelling at a given degree of cross-linking are in reasonable agreement with each other. However the entropy components of the modulus and the sub-chain density calculated from swelling measurements are appreciably greater than those calculated from cross-linking or from direct mechanical measurements. They increase linearly with cross-linking. It is concluded that the number of sub-chains effective in limiting swelling is greater than that effective in direct mechanical mea

surements.

Theory of flow-induced fibril formation in polymer solutions, J. D. Hoffman, J. Res. Nat. Bur. Stand. (U.S.), 84, No. 5, 359384 (Sept.-Oct. 1979).

Key words: core fibril; cumulative stress; flow-induced crystallization; nucleation theory; polyethylene; polymer fiber; shish; volume strain.

A treatment of the formation of a basic core fibril (shish) of the type that is generated by flow-induced crystallization of a polymer from solution is given that features the concept of cumulative strain. Multiple nucleation acts by flow-elongated molecules produce an empbryonic fibril that is a connected set of bundlelike nuclei. Surface stress resulting from repulsion of the quasi-random coil chains in the amorphous zone between the nuclei or crystallites builds up at the bundle ends as the nuclei mature, leading ultimately to a high end surface free energy, and to volume strain in the crystallites comprising the core fibril. The theory leads to a stable (or metastable) fibril diameter a, and mean characteristic length 1, with a fixed axial ratio, and predicts why the diameter does not grow further even in a medium that is supersaturated with polymer. The predicted dependence of a,, l,, and the axial ratio, on undercooling is in approximate agreement with experiment. The lattice expansion in the crystal resulting from volume strain is also in fair accord with experiment. The effect of annealing, including the commonly encountered case where the volume strain relaxes to give normal lattice dimensions, but with a high end surface energy still remaining, is noted. The effect of volume strain and the distribution of core fibril lengths about 1, on the melting behavior is calculated. The theory can reproduce crystallinity versus temperature data on polyethylene fibrils. This procedure yields an independent value of I,. The overall treatment implies that the core fibril is a set of concatenated and substantially extended-chain crystallites with bundlelike ends and a somewhat expanded lattice when unannealed and under tension, the molecular connections between the crystallites consisting of short amorphous ciliary bridges. It is suggested that prolonged annealing at high temperatures can a substantial number of the amorphous zones.

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Observations of surface changes in platinum crucibles, C. P. Saylor, E. Wichers, and J. I. Hoffman, J. Res. Nat. Bur. Stand. (U.S.), 84, No. 5, 385-394 (Sept.-Oct. 1979).

Key words: contrast augmentation of reflecting surfaces; double-diaphragm; faces (crystal) on platinum crucibles; hematite forming on platinum; iron as alloy in platinum; platinum ware; surface of platinum influenced by method heating.

Ion which has been in solid solution in a platinum crucible will cause iron determinations in analyses to become high. Likewise the iron, oxidizing to ferric oxide during ignition, segregates along the boundaries between platinum crystals. It causes embrittlement and eventual crumbling of the crucible.

During these studies it was observed that after heating in an electric muffle furnace the surface of a crucible was covered by tiny crystallographic faces. When, however, heating to the same temperature was carried out in a gas flame the facets almost smoothed out of existence.

Isoionic isotope exchange with hydroxylapatite and the dilution effect, D. N. Misra, J. Res. Nat. Bur. Stand. (U.S.), 84, No. 5, 395-406 (Sept.-Oct. 1979).

Key words: dilution effect, at same pH and concentration; hydration shell, role of; hydroxylapatite, at different pHs; isotopic exchange, isoionic; recrystallization, role of; surface layer, role of.

Isoionic isotope exchange data of 45Ca2+ and 32PO3 in a saturated solution with hydroxylapatite at 25 °C, collected by Avnimelech, have been reinterpreted on the basis that the processes consisted of three pools: hydration shell, surface layer and "recrystallization of crystallites." These processes are regarded as strictly separable. This theoretically allows: (i) a quantitative evaluation of the constants involved in the processes; (ii) an estimation of the exchange capacities of hydration and surface layers (fast pools) which may be pH-dependent; and (iii) a determination of the isoionic exchange rate constants. The constants are essentially the same for Ca2+ and PO, at a given pH if the cross-sectional areas of the ions are taken as 23 Å2 and 33 Å2 respectively; they, perhaps, increase linearly with the hydrogen ion concentration of the solutions.

The effects of three consecutive abrupt dilutions of the radioactive ions without changing the concentrations (or pH) of the nonradioactive components of the solution are predictable by a mathematical model based on the complete reversibility of the two fast pools and the kinetics of the irreversible third pool.

November-December 1979

Molecular dynamics study of liquid rubidium and the LennardJones fluid, R. D. Mountain and S. W. Haan, J. Res. Nat. Bur. Stand. (U.S.), 84, No. 6, 439-446 (Nov.-Dec. 1979).

Key words: intermediate scattering function; LennardJones liquid; liquid rubidium; molecular dynamics; radial distribution function; transverse current correlation function; velocity autocorrelation function.

Molecular dynamics calculations were made for three thermodynamic states of a model of liquid rubidium and for two states of the Lennard-Jones fluid in order to investigate the influence of density, temperature and interatomic potential on the spectra of density fluctuations in these fluids. Here the results for the intermediate scattering function, the radial distribution function, the velocity autocorrelation function of the transverse momentum autocorrelation function are presented in tabular form. The procedures employed in this study are discussed and the major features of these functions are described.

Room temperature poling of poly(vinylidene fluoride) with deposited metal electrodes, J. M. Kenney and S. C. Roth, J. Res. Nat. Bur. Stand. (U.S.), 84, No. 6, 447-453 (Nov.-Dec. 1979).

Key words: dielectric strength; electrets; piezoelectricity; polarization; poling procedures; polymers; poly(vinylidene fluoride); pyroelectricity; transducers.

High values of pyroelectric and piezolectric activity in fullyelectroded films of poly(vinylidene fluoride) were obtained by "conventional" (non-corona) poling at room temperature with sufficiently high fields. The avoidance of breakdown while obtaining high activity requires an understanding of the time dependence of both breakdown and activity. Time-to-breakdown as a function of field, and room-temperature pyroelectric activity (7-14 days after poling at 23.5 °C) as a function of poling time and field were obtained for 25-μm biaxially stretched films with evaporated aluminum electrodes. The highest activities

were obtained by poling at the highest fields and poling to breakdown. A pyroelectric activity of 36 μCK-1m2 was measured two weeks after poling with a nominal field of 550 MVm-1 for a nominal poling time of 10 s (reduced by multiple breakdown). The highest activity obtained with no apparent breakdown (31 μCK ̄1m ̄2) was measured a week after poling with a field of 400 MVm-1 for 10 s. These values are comparable with the highest that have been reported for this material using any poling temperature or using corona poling. Generators for discrete polynomial L, approximation problems, P. Domich, J. Lawrence, and D. Shier, J. Res. Nat. Bur. Stand. (U.S.), 84, No. 6, 455-488 (Nov.-Dec. 1979).

Key words: algorithm testing; approximation; computational experiment; least absolute deviation; polynomial approximation; test problems.

Polynomial approximation problems represent a class of specially structured problems which are frequently encountered in empirical curve-fitting. Two generators for creating such problems have been developed, implemented and used in the testing of discrete L, approximation codes. Both generators permit automatic generation of problems with specified characteristics and (for one generator) having known, unique and controllable solutions.

A graph coloring algorithm for large scheduling problems, F. T. Leighton, J. Res. Nat. Bur. Stand. (U.S.), 84, No. 6, 489-506 (Nov.-Dec. 1979).

Key words: algorithm; chromatic number; color function; graph; graph coloring; heuristic; interchange; random test graphs; scheduling; time complexity.

A new graph coloring algorithm is presented and compared to a wide variety of known algorithms. The algorithm is shown to exhibit O(n2) time behavior for most sparse graphs and thus is found to be particularly well suited for use with large-scale scheduling problems. In addition, a procedure for generating large random test graphs with known chromatic number is presented and is used to evaluate heuristically the capabilities of the algorithms discussed.

This journal is published quarterly by the American Chemical Society and the American Institute of Physics for the National Bureau of Standards. The objective of the Journal is to provide critically evaluated physical and chemical property data, fully documented as to the original sources and the criteria used for evaluation. Critical reviews of measurement techniques, whose aim is to assess the accuracy of available data in a given technical area, are also included. The principal source for the Journal is the National Standard Reference Data System (NSRDS). The Journal is not intended as a publication outlet for original experimental measurements such as are normally reported in the primary research literature, nor for review articles of a descriptive or primarily theoretical nature.

Volume 8, No. 1

Energy levels of titanium, Ti 1 through Ti xxII, C. Corliss and J. Sugar, J. Phys. Chem. Ref. Data 8, No. 1, 1-62 (1979).

Key words: atomic energy levels; atomic spectra; titanium. The energy levels of the titanium atom in all of its stages of ionization, as derived from the analyses of atomic spectra, have been critically compiled. In cases where only line classifications are reported in the literature, level values have been derived. Term designations, experimental g-values, and ionization energies are included. Calculated percentages of the two leading components of the eigenvectors of the levels are given.

The spectrum and energy levels of the neutral atom of boron (B 1), G. A. Odintzova and A. R. Striganov, J. Phys. Chem. Ref. Data 8, No. 1, 63-68 (1979).

Key words: atomic energy levels; atomic spectra; boron. The published data on the spectrum of the neutral atom of boron are compiled and presented. In one table 164 lines in the range 36010-993 Å are listed with their intensities and classifications. A second table gives 92 levels with the numerical values of the energy.

Relativistic atomic form factors and photon coherent scattering cross sections, J. H. Hubbell and I. Øverbø, J. Phys. Chem. Ref. Data 8, No. 1, 69-106 (1979).

Key words: atomic form factor; coherent scattering; cross sections; gamma rays; photons; Rayleigh scattering; tabulations; x rays.

Tabulations are presented of relativistic Hartree-Fock atomic form factors F(x,Z), for values of x(=sin(8/2)/λ from 0.01 to 10° Å-1, for all elements Z = 1 to 100. For Z = 1, F(x,Z) is given by the exact expression of Pirenne. For Z = 2 to 98, x = 0.01 to 2.0 Å ̈1, the tabulated values are those of Cromer and Waber given in the International Tables for X-Ray Crystallog-` raphy (Vol. IV, 1974), based in part on the work of Doyle and Turner. For Z = 21 to 92, x = 2.2 to 6.0 Å1, the present tables are based on the values of Doyle and Turner and additional values (Z = 44, 60, 68, and 74) as given by Øverbø. For Z = 3 to 20, x = 2.2 to 45 Å-1, and Z = 21 to 92, x = 6.2 to 45 Å-1 the tables are interpolated from values given for 36 elements by Øverbø, extended to x = 10o Å-1 using Øverbø's corrections to the Bethe-Levinger K-shell expression. The remainder of the table is filled in by interpolation and extrapolation, guided for high x-values by the Bethe-Levinger result. Tables of relativistic

coherent (Rayleigh) scattering cross sections, obtained by numerical integration of the Thomson formula weighted by F(x,Z), are presented for all elements Z=1 to 100, for photon energies 100 eV (λ = 124 Å = 12.4 nm) to 100 MeV (A = 0.000 124 Å = 12.4 fm). Departures from the nonrelativistic coherent scattering cross sections tabulated in J. Phys. Chem. Ref. Data 4, 471 (1975) are less than 1% for Z 20. However for a high-Z element such as lead, for example, the relativistic coherent scattering cross section is systematically higher by less than 0.4% below 1 keV, by 8% at 100 keV and by 13% above 1 MeV.

Microwave spectra of molecules of astrophysical interest. XIV. Vinyl cyanide (Acrylonitrile), M. C. L. Gerry, K. Yamada, and G. Winnewisser, J. Phys. Chem. Ref. Data 8, No. 1, 107124 (1979).

Key words: interstellar molecules; microwave spectra; molecular parameters; radio astronomy; rotational transitions; vinyl cyanide.

The available data of the microwave spectrum of vinyl cyanide are critically reviewed and tabulated. Molecular data such as rotational constants, centrifugal distortion constants, hyperfine coupling constants, dipole moments, and structural parameters are tabulated. Rotational transitions from 400 MHz to 200 GHz, which are likely to be of interest to radio astronomy, are calculated and tabulated along with their estimated 95% confidence limits.

Molten salts: Volume 4, Part 4. Mixed halide melts, G. J. Janz, R. P. T. Tomkins, and C. B. Allen, J. Phys. Chem. Ref. Data 8, No. 1, 125-302 (1979).

Key words: bromides; chlorides; data compilation; density; electrical conductance; fluorides; halides; iodides; molten salt mixtures; standard reference data; surface tension; viscosity.

Data on the electrical conductance, density, viscosity, and surface tension of mixed halide melts have been systematically collected and evaluated. Results are given for eighty-five binary mixtures over a range of compositions and temperatures.

Volume 8, No. 2

Atomic radiative and radiationless yields for K and L shells, M. O. Krause, J. Phys. Chem. Ref. Data 8, No. 2, 307-328 (1979).

Key words: atomic properties; Auger yield; Coster-Kronig yield; effective fluorescence yield; fluorescence yield; K shell; L shell; non-radiative yield; partial level width; radiative yield.

The available body of information on (a) fluorescence, Auger, and Coster-Kronig yields, (b) radiative and radiationless transition rates, (c) level widths, (d) x-ray and Auger line widths, (e) x-ray and Auger spectra, and (f) Coster-Kronig energies has been used to generate an internally consistent set of values of atomic radiative and radiationless yields for the K shell (5≤ Z ≤ 110) and the L subshells ( 1 2 ≤ Z ≤ 1 10). Values Coster-Kronig yields f1, fia, fia, fia, fia. Auger yields aƒ, a1, a,, aɔ, and effective fluorescence yields v, and v, are presented in tables and graphs.

of fluorescence yields wx. @ 1.

Estimates of uncertainties are given. Updated and expanded graphs of partial and total widths of K, L1, L2, and L3 levels are presented as well as a reference list of papers published since about 1972.

Natural widths of atomic K and L levels, Ka x-ray lines and several KLL Auger lines, M. O. Krause and J. H. Oliver, J. Phys. Chem. Ref. Data 8, No. 2, 329-338 (1979).

Key words: Auger effect; Auger line width; K shell; level width; line width; L shell; natural width; x-ray line width. Semi-empirical values of the natural widths of K, L1, L2 and L levels, Ka, and Ka, x-ray lines, and KL1L1, KL1L2 and KL2L Auger lines for the elements 10 ≤ Z ≤ 110 are presented in tables and graphs. Level width_ F1(i = K, L1, L2, Lз) is obtained from the relation_г1 = FR./w, using the theoretical radiative rate T. from Scofield's relativistic, relaxed Hartree-Fock calculation and the fluorescence yield w, from Krause's evaluation. X-ray and Auger line widths are calculated as the sums of pertinent level widths. This tabulation of natural level and line

widths is internally consistent, and is compatible with all relevant experimental and theoretical information. Present semiempirical widths, especially those of Ka, and Ka2 x-rays, are compared with measured widths. Uncertainties of semi-empirical values are estimated.

Electrical resistivity of alkali elements, T. C. Chi, J. Phys. Chem. Ref. Data 8, No. 2, 339-438 (1979).

Key words: alkali elements; cesium; electrical resistivity; francium; lithium; magnetic flux density dependence; potassium; pressure dependence; rubidium; sodium; temperature dependence.

This paper presents and discusses the available data and information on the electrical resistivity of alkali elements (lithium, sodium, potassium, rubidium, cesium, and francium) and contains recommended reference values (or provisional or typical values). The compiled data include all the experimental data available from the literature and cover the temperature dependence, pressure dependence, and magnetic flux density dependence. The temperature range covered by the compiled data is from cryogenic temperatures to above the critical temperature of the elements. The recommended values are generated from critical evaluation, analysis, and synthesis of the available data and information and are given for both the total electrical resistivity and the intrinsic electrical resistivity. For most of the elements, the recommended values cover the temperature range from 1 K to 2000 K.

Electrical resistivity of alkaline earth elements, T. C. Chi, J. Phys. Chem. Ref. Data 8, No. 2, 439-498 (1979).

Key words: alkaline earth elements; barium; beryllium; calcium; electrical resistivity; magnesium; radium; strontium; temperature dependence.

This paper presents and discusses the available data and information on the electrical resistivity of alkaline earth elements (beryllium, magnesium, calcium, strontium, barium, and radium) and contains recommended or provisional reference values. The compiled data include all the experimental data available from the literature. The temperature range covered by the compiled data is from cryogenic temperatures to above the melting temperature of the elements. The recommended values are generated from critical evaluation, analysis, and synthesis of the available data and information and are given for both the total electrical resistivity and the intrinsic electrical resistivity. For most of the elements, the recommended values cover the temperature range from 1 K to 1000 K.

Vapor pressures and boiling points of selected halomethanes, A P. Kudchadker, S. A. Kudchadker, R. P. Shukla, and P. R Patnaik, J. Phys. Chem. Ref. Data 8, No. 2, 499-518 (1979).

Key words: Antoine equation; enthalpy of vaporization; halomethanes; vapor pressure-boiling point data; Wagner equation.

This critical review is a study of the vapor pressure-boiling point data from the triple point to the critical point for CH1aXa (X = Br, I) and CH1a+b+c+α) FaCl Brel, halomethanes The available data are carefully analyzed and the "best" data selected. The selection procedure is discussed. Uncertainties in the selected temperatures and pressures are reported. The selected data were fitted to the Antoine equation for data up to 1500 mm Hg pressure and the Wagner equation for data up to the critical point. Antoine constants for nineteen compounds and the Wagner constants for five compounds are reported. The enthalpy of vaporization at 298.15 K and at the normal boiling point have been computed.

Ideal gas thermodynamic properties of selected bromoethanes and iodoethane, S. A. Kudchadker and A. P. Kudchadker, J. Phys. Chem. Ref. Data 8, No. 2, 519-526 (1979).

Key words: bromoethanes; ideal gas thermodynamic properties; internal rotation; iodoethane; potential barrier heights; symmetric top; torsional frequencies.

The available molecular parameters, fundamental frequencies, potential barrier heights, torsional frequencies, and standard enthalpies of formation at 298.15 K for selected bromoethanes and iodoethane containing one symmetric-top group have been critically evaluated and recommended values selected. The chemical thermodynamic properties in the ideal gas state at one atmosphere pressure using the rigid-rotor harmonic-oscillator approximation have been calculated for CH,CH,Br, CH,CHBг2, CH,CBг ̧, С,Bг, and CH,CH,I. The internal rotational contributions have been obtained from the partition function formed by the summation of internal rotation energy levels.

Thermodynamic properties of normal and deuterated naphthalenes, S. S. Chen, S. A. Kudchadker, and R. C. Wilhoit, J. Phys. Chem. Ref. Data 8, No. 2, 527-536 (1979).

Key words: enthalpy of formation; ideal gas thermodynamic properties; molecular structure; normal and deuterated naphthalenes; vibrational assignments.

Structural and spectroscopic data and the standard enthalpy of formation at 298.15 K for C10Hs, a-C10H ̧D1, ß-C10H‚D ̧, and CoD were reviewed. The selected values were utilized to calculate the ideal gas thermodynamic properties in the temperature range 0 to 1500 K, using the rigid rotor and harmonic oscillator model. The comparison between the third law entropies and the spectroscopically calculated entropies of C1H, was studied. The agreement is satisfactory within the experimental uncertainties.

Microwave spectra of molecules of astrophysical interest. XV. Propyne, A. Bauer, D. Boucher, J. Burie, J. Demaison, and A. Dubrulle, J. Phys. Chem. Ref. Data 8, No. 2, 537-558 (1979).

Key words: interstellar molecules; line strengths; microwave spectra; molecular constants; propyne; radio astronomy; rotational transitions.

The microwave spectrum of propyne is critically reviewed for information applicable to radio-astronomy. Molecular data such as the derived rotational constants, centrifugal distortion parameters, hyperfine coupling constants, electric dipole mo

ment, and molecular structure are tabulated. The observed rotational transitions are presented for the astronomically interesting isotopic forms and the lowest lying vibrational state of propyne. Calculated rotational transitions are presented for the ground vibrational state of 12CH2 12C = "CH, 13CH, 12C = 12CH, 12CH, 13C = 12CH and "CH, 12C = "CH, and for the vibrationally excited state v10 of 12CH3 12C = 12CH.

A correlation of the viscosity and thermal conductivity data of gaseous and liquid propane, P. M. Holland and H. J. M. Hanley, J. Phys. Chem. Ref. Data 8, No. 2, 559-576 (1979).

Key words: correlated data; critical point enhancement; data evaluation; propane; thermal conductivity; viscosity. Data for the viscosity and thermal conductivity of gaseous and liquid propane have been evaluated and represented by empirical functions developed in previous work. Tables of values are presented for the range 140-500 K for pressures to 50 MPa (≈ 500 atm). The viscosities are estimated to have uncertainties of about ± 5%, with corresponding uncertainties of the thermal conductivities of about ± 8%. It is stressed that the data base should be improved. As in our work with other fluids, the anomalous contribution to the thermal conductivity in the vicinity of the critical point is included.

Volume 8, No. 3

Microwave spectra of molecules of astrophysical interest. XVI. Methyl formate, A. Bauder, J. Phys. Chem. Ref. Data 8, No. 3, 583-618 (1979).

Key words: internal rotation; interstellar molecules; line strengths; methyl formate; microwave spectrum; radio astronomy; rotational transitions.

The microwave spectrum of methyl formate is critically reviewed for information applicable to radio astronomy. The review is based on new laboratory measurements in the frequency range from 8 GHz to 58 GHz. Molecular data such as the derived rotational constants, centrifugal distortion parameters, internal rotation parameters, electric dipole moment and molecular structure are tabulated. Since the primary objective is to provide microwave spectral transitions applicable to radio astronomy observations, the review encompasses only the ground state rotational spectrum of the most abundant isotopic form of methyl formate, H1CO,"CH,. While all measured transitions are included, the predicted transitions were limited to J ≤ 12 in the range of 900 MHz to 250 GHz.

Molecular structures of gas-phase polyatomic molecules determined by spectroscopic methods, M. D. Harmony, V. W. Laurie, R. L. Kuczkowski, R. H. Schwendeman, D. A. Ramsay, F. J. Lovas, W. J. Lafferty, and A. G. Maki, J. Phys. Chem. Ref. Data 8, No. 3, 619-722 (1979).

Key words: bond angles; bond distances; gas-phase polyatomic molecules; gas-phase spectroscopy; microwave spectroscopy; molecular conformation; molecular spectroscopy; molecular structure; molecules; structure. Spectroscopic data related to the structures of polyatomic molecules in the gas phase have been reviewed, critically evaluated, and compiled. All reported bond distances and angles have been classified as equilibrium (r), average (r,), substitution (r,), or effective (r.) parameters, and have been given a quality rating which is a measure of the parameter uncertainty. The surveyed literature includes work from all of the areas of gas-phase spectroscopy from which precise quantitative structural information can be derived. Introductory material includes definitions of the various types of parameters and a description of the evaluation procedure.

Critically evaluated rate constants for gaseous reactions of several electronically excited species, K. Schofield, J. Phys. Chem. Ref. Data 8, No. 3, 723-798 (1979).

Key words: activation energies; electronically excited states; evaluation; gaseous interactions; molecular correlations; quenching; radiative lifetimes; rate constants; reactive channels; recommended data; relaxation processes; review.

An extensive evaluation is presented of the available gas phase chemical kinetic rate constants for the interactions of the low lying electronic states of several atoms and molecules with numerous collision partners. These include the following excited states: C(2'D2,2'S), N(2aD3/2.5/2,22P1/2.3/2), P(32D3/2. 5/2,32P1/2.3/2), S(31D2,31So), Se(43Po.41D2,41So), Te(53P1.0,5'D2, 5'S), CO(a3П‚a'3Σ*, ƒA‚e3Σ ̄‚Â1), CS(@3‚Â1), OH(43Σ*), OD(A2Σ*), Or(c1Σu ̄‚C®a...‚Æ3Σ„*‚Â3Σ ̧ ̄), and S2(a1A,,b1Σ,*‚A 3Σ*,B3Σ ̄). Wherever possible, recommended values are suggested. Much of the data refers only to room temperature. To facilitate the evaluation, collision-free radiative lifetimes often have been required. These also have been evaluated and are presented. The mechanisms of the interactions and the various potential kinetic channels are discussed. These include such processes as chemical reactions, electronic quenching to the ground electronic state, electronic cross relaxation to an adjacent excited state, and for molecules, vibrational and rotational relaxation processes within the excited state. A complete coverage of the literature published prior to 1978 has been attempted.

A review, evaluation, and correlation of the phase equilibria, heat of mixing, and change in volume on mixing for liquid mixtures of methane + ethane, M. J. Hiza, R. C. Miller, and A. J. Kidnay, J. Phys. Chem. Ref. Data 8, No. 3, 799-816 (1979).

Key words: binary mixtures; data correlation; excess
volumes; heat of mixing; liquid-vapor equilibria; methane
+ ethane.

The available experimental data for liquid equilibria, heat of mixing, and change in volume on mixing for the methane + ethane system have been reviewed and where possible evaluated for consistency. The derived properties chosen for analysis and correlation were liquid mixture excess Gibbs energies, Henry's constants, and K values. Data sets, selected on the basis of the consistency tests applied, were correlated as functions of temperature and composition to provide internally consistent sets of property values suitable for engineering design calculations.

Energy levels of aluminum, Al 1 through Al xш, W. C. Martin and R. Zalubas, J. Phys. Chem. Ref. Data 8, No. 3, 817-864 (1979).

Key words: aluminum; atomic energy levels; atomic spectra; electron configurations; ionization potentials.

Energy level data are given for the atom and all positive ions of aluminum (Z= 13). These data have been critically compiled, mainly from published material on measurements and analyses of the optical spectra. We have derived or recalculated the levels for a number of the ions. In addition to the level value in cm-1 and the parity, the J value and the configuration and term assignments are listed if known. Leading percentages from the calculated eigenvectors are tabulated wherever available. Ionization energies are given for all spectra.

Energy levels of calcium, Ca 1 through Ca xx, J. Sugar and C. Corliss, J. Phys. Chem. Ref. Data 8, No. 3, 865-916 (1979).

Key words: atomic energy levels; atomic spectra; calcium energy levels.