cantly more sensitive to the presence of voids in die attachment than steady-state thermal resistance, and development of a simplified circuit for screening transistors for susceptibility to hotspot formation by the current-gain technique. Work is continuing on measurement of resistivity of semiconductor crystals; study of gold-doped silicon; specification of germanium for gamma-ray detectors; evaluation of wire bonds and die attachment; measurement of thermal properties of semiconductor devices, transit time and related carrier transport properties in junction devices, and electrical properties of microwave devices; and characterization of silicon nuclear radiation detectors. Supplementary data concerning staff, standards committee activities, technical services, and publications are included as appendixes.

TN703. ARPA-NBS program of research on high temperature materials and laser materials, reporting period January 1 to June 30, 1971, A. D. Franklin and H. S. Bennett, Editors, Nat. Bur. Stand. (U.S.), Tech. Note 703, 39 pages (Dec. 1971).

Key words: Al2O3; crystal growth; damage threshold; glass; high temperature materials; laser; oxides; oxygen diffusion; pure materials; sapphire.

Progress reports are given for projects on the growth of ultra

pure Al2O3 crystals, the development of a mass spectrometerbased sectioning technique for measuring oxygen diffusion in oxides and the development of a precision facility for measuring the threshold energy in a laser beam producing damage in a transparent substance.

TN708. Interlaboratory evaluation of smoke density chamber, T. G. Lee, Nat. Bur. Stand. (U.S.), Tech. Note 708, 80 pages (Dec. 1971).

Key words: Building materials; fire tests; interlaboratory tests; optical density; round robin; smoke; smoke density chamber; statistical analysis.

Results are reported of an interlaboratory (round-robin) evaluation of the smoke density chamber method for measuring the smoke generated by solid materials in fire. A statistical analysis of the results from 10 material-condition combinations and 18 laboratories is presented. For the materials tested, the median coefficient of variation of reproducibility was 7.2 percent under non-flaming exposure conditions and 13 percent under flaming exposure conditions. A discussion of errors and recommendations for improved procedures based on user experience is given. A tentative test method description is included as an appendix.

Practical information, based on NBS research and experience, covering areas of interest to the consumer. Easily understandable language and illustrations provide useful background knowledge for shopping in today's technological marketplace.

CIS4. Facts about hearing and hearing aids, E. L. R. Corliss,

Nat. Bur. Stand. (U.S.), Consum. Inf. Ser. 4, 35 pages (Nov. 1971).

Key words: Audition; communications; hearing; hearing aids; selection of hearing aids; speech communication.

A consumers information publication containing information on hearing aids including selection, use, and maintenance.

11798. Brauer, G. M., Pyrolysis-gas chromatographic techniques

for polymer identification, Chapter 2 in Thermal Characteristics Techniques in Techniques and Methods of Polymer Evaluations, P. Slade, ed., II, 41-105 (Marcel Dekker Publ., New York, N.Y., 1970).

Key words: Chromatographic analysis of degradation products; polymer characterization; polymer identification; pyrolysis-gas chromatography of polymers; pyrolytic techniques.

Pyrolytic techniques used in conjunction with gas chromatography are very useful for elucidating the structure of macromolecules. These methods are a powerful tool in the qualitative characterization of the gross structure, the study of the thermal stability of polymers and the identification of their pyrolysis products, but have also found an increasing number of applications for the quantitative analysis of copolymeric systems and in studies of the kinetics of polymer degradation. The shape of the pyrograms is dependent on the structural characteristics such as the degree of branching or crosslinking, stereoregularity, crystallinity, and monomer sequence length distribution in block and graft copolymers. Thus the pyrolysis-gas chromatographic technique opens up new avenues in studying the ultimate arrangement of monomeric units within the polymer chain.

11799. Berger, M. J., Seltzer, S. M., Bremsstrahlung and photoneutrons from thick tungsten and tantalum targets, Phys. Rev. C 2, No. 2, 621-631 (Aug. 1970).

Key words: Bremsstrahlung; bremsstrahlung efficiency; Monte Carlo; photon neutron; radiation transport; thick targets.

Monte Carlo calculations have been made of electron-photon cascades in thick tungsten targets bombarded by electrons with energies up to 60 MeV. The following information has been obtained: (1) the bremsstrahlung efficiency, (2) the angular distribution of the emitted bremsstrahlung intensity, (3) the spectra of the bremsstrahlung emitted in various directions, (4) the transmission of primary and secondary electrons through the target, (5) energy deposition as function of the depth in the target, (6) the differential photon track length distribution inside the target, and (7) the yield of photoneutrons. The paper also includes various comparisons with experimental data.

Optical observations, in which a microscope was used with the diamond-anvil pressure cell, were carried out on benzene, naphthalene, and anthracene up to temperatures of about 600 °C and pressures of approximately 40 kilobars. New high-pressure phases of benzene (benzene III) and anthracene (anthracene 11) were observed, and the existence of the high-pressure polymorph, naphthalene II, was verified. All three materials decompose initially to a reddish-orange liquid, and ultimately to amorphous carbon. The decomposition temperatures decrease with increasing molecular size.

11801. Borie, E., Radiative corrections to back scattering, Phys. Rev. C 2, No. 2, 770-771 (Aug. 1970).

Key words: Anomalous moment; back scattering; electron; radiative correction.

It is shown that the anomalous magnetic moment of the electron contributes to the radiative correction to scattering by a charge, even at high energies, when the scattering angle is 180°. This effect increases the radiative correction slightly as compared with the usual Schwinger correction.

11802. Bowen, R. L., Crystalline dimethacrylate monomers, J. Dental Res. 49, No. 4, 810-815 (July-Aug. 1970).

Key words: Biomaterials; dimethacrylates; phthalate monomers; purification methods; resins for composites; ternary eutectic; thermosetting monomers.

Certain dimethacrylate monomers can be prepared and purified by recrystallization. On mixing, the crystals liquefy by forming a ternary eutectic. The colorless oily liquid is suitable for use in composite formulations.

11803. Candela, G. A., Spin relaxation process of chromium ion in potassium alum, J. Chem. Phys. 52, No. 7, 3754-3757 (Apr. 1, 1970).

Key words: Chromium alum; spin-lattice relaxation. The electron spin relaxation process of potassium chrome alum and potassium chrome aluminum alum was investigated at 14.5 GHz by measuring the change in the static dc magnetization as a function of the cw microwave power absorbed at electron resonance. At liquid-helium temperatures, the direct spin-lattice relaxation process is the dominant rate-determining process for magnetically dilute potassium chrome aluminum alum, but for the magnetically concentrated crystals, the spin-lattice process can easily be obscured by the lattice-bath relaxation process. The spin-lattice relaxation measurements at 14.5 GHz and those of other workers at 9 GHz are in agreement with the calculations made by Van Vleck in 1940.

11804. Ensign, T. C., Chang, T. T., Kahn, A. H., Hyperfine and nuclear quadrupole interactions in copper-doped TiO2, Phys. Rev. 188, No. 2, 703-709 (Dec. 10, 1969).

Key words: Copper; EPR; g-factors; hyperfine interaction; quadrupole coupling; rutile; titanium dioxide.

Single crystals of TiO2: Cư2+ have been investigated at 20 K using the technique of electron paramagnetic resonance. The major features of the EPR spectra can be attributed to divalent copper (3d) in substitutional (Ti1+) sites. Information has been gained about both isotopes of copper and about the interactions which concern this ion. For the substitutional site, the spinHamiltonian parameters in the S = 1/2, 1 = 3/2 manifold are: gø 2.109, gy=2.094, gz= 2.346, A 63+18.7 × 10-4 cm-1, 4,63 + 27.2 × 10-4 cm-1, A63 - 87.5 × 10-4 cm-1, A65+18.8 × 10-4 cm1, A65+28.7 × 10-4 cm-1, A265 - 93.7 × 10-4 cm-1, P= 2.56 × 10-4, P= 2.37 × 10-4, and P2+4.93 × 10-4 cm-1. The magnitudes and relative signs of these parameters have been determined experimentally, while the absolute signs have been predicted theoretically from a model which gives a

consistent picture of the ordering of the d electronic states. In addition, the theoretical treatment gives a satisfactory estimate of P. Departure from tetragonality was taken into account. The covalency parameter a2 which measures the fraction of the hole wave function on the Cu2+ ion is found to be 0.71, and the factor K giving rise to isotropic hyperfine structure is found to be 0.31. 11805. Ensign, T. C., Stokowski, S. E., Shared holes trapped by charge defects in SrTiO3, Phys. Rev. B 1, No. 6, 2799-2810 (Mar. 15, 1970).

=

Key words: Color centers; EPR; hole centers; optical absorption; shared holes; SrTiO3.

Using the techniques of EPR and optical irradiation in conjunction with optical-absorption measurements, we have gained useful information about the nature of some hole centers in SrTiO3. Primarily, we have investigated, at temperatures near 77 K, single crystals doped with aluminum. Two principal centers have been explored: (1) the Al-O center - a hole shared among the oxygens which surround Al3+, and (2) the X-O- center-a hole shared in a similar fashion, but more deeply trapped by a charge defect of unknown origin. The Al-O- center arises after band-gap irradiation and is characterized at 77 K by the following g values and hyperfine constants: gn=2.0137, g1=2.0124, A 8.3 x 104 cm', and A=7.6 × 10 cm-1. The X-Ocenter is present before optical irradiation. No hyperfine structure is observed, but the isotropic g value is 2.0130 at all temperatures from 4.2 to 300 K. An 800-nm absorption band arising after band-gap excitation has been correlated with the Al-Ocenter. 430- and 600-nm absorption bands have been correlated with the absence of Fe3+ in the EPR spectrum, and a 500-nm band has also been observed. In addition, the role of iron in the photochromic processes of SrTiO, is presented. Finally, theoretical work utilizing the molecular orbital σ and π states in On symmetry has provided a firm basis for the sharing model. The experimental g values and hyperfine constants are discussed in light of this model and are found to be in good agreement. 11806. Evans, W., Garvin, D., The evaluator versus the chemical literature, J. Chem. Doc. 10, No. 3, 147-150 (1970).

Key words: Abstracts; chemistry; content of articles; data; description of experiments; evaluation of data; numerical data; publication standards; titles.

The presentation of quantitative experimental results is discussed from the viewpoint of the evaluator of data. The principal needs are a detailed description of the experimentation and numerical results suitable for reanalysis. Suggestions are made for the improvement of the content of chemical papers and the retrieval of the results. Content may be improved by preparing guides that state the minimum acceptable detail for various types of measurements. Retrieval may be enhanced by judicious editing of titles and abstracts.

11807. Feldman, A., Brower, W. S., Jr., Horowitz, D., Optical activity and Faraday rotation in bismuth oxide compounds, Appl. Phys. Letters 16, No. 5, 201-202 (Mar. 1, 1970).

Key words: Bi34Ga2O54; Bi12GeO20; Bi12SiO20; Bi12TiO20; BiZnO22; Faraday effect; modulator materials; optical activity; optical rotatory power; Verdet coefficient.

The optical rotatory power and Faraday rotation were measured in crystals of 17Bi2O3: Ga2O3, 7Bi2O3: ZnO, B12 TiO20, Bi12GeO20, and Bi12SiO20 in the wavelength range 400 to 700 nm at room temperature. Our crystals were enantiomorphs of those reported previously. The large Verdet coefficients indicate that these crystals are potentially useful as magneto-optic modulator materials.

11808. Feldman, A., Kahn, A. H., Landau diamagnetism from the coherent states of an electron in a uniform magnetic field, Phys. Rev. B 1, No. 12, 4584-4589 (June 15, 1970).

Key words: Coherent states; diamagnetism; electron in a magnetic field.

A complete set of coherent-state wave packets has been constructed for an electron in a uniform magnetic field. These states are nonspreading packets of minimum uncertainty that follow the classical motion. Use was made of the ladder operators that generate all the eigenstates of the Hamiltonian from any one energy eigenstate. The coherent states are the eigenstates of the two ladder operators that annihilate the zero-angular-momentum ground state. We have calculated the partition function, exploiting advantages of the coherent-state basis. The Landau diamagnetism and the de Haas-van Alphen oscillations are contained in the coherent-state framework.

11809. Frederikse, H. P. R., Comments on electronic transport in transition metal oxides, J. Res. Develop. 14, No. 3, 295-300 (May 1970).

Key words: Electronic transport; LaCoO3; magnetic ordering; transition metal oxides.

Several aspects of electronic transport in nonmagnetic and magnetic transition metal oxides are reviewed. These include high- and low-temperature measurements of conductivity, the Hall effect and the Seebeck effect, and their analysis in terms of the electronic energy structure. Particular emphasis is put on the temperature dependence of the Hall mobility, which gives essential information concerning the correct description of the energy states and the scattering of the charge carriers. The second half of the paper discusses the relation between the transport properties and the magnetic ordering. The properties of LaCoO3 together with an interpretation suggested by Goodenough are presented to illustrate this point.

11810. Goldstein, J. I., Henderson, E. P., Yakowitz, H., Investigation of lunar metal particles, (Proc. Apollo 11 Lunar Science Conf., January 1970, Houston, Texas), Geochim. Cosmochim. Acta 1, 499-512 (1970).

Key words: Electron probe microanalysis; lunar samples; lunar simulation; lunar thermal history; meteorites; scanning electron microscopy.

Several metallic particles from lunar fine samples 10084 and 10085-17M and from breccia sample 10046-18A were investigated by means of optical microscopy, scanning electron microscopy, and electron probe microanalysis. These particles consisted of two large globules, metal spread on glassy spheres, fragments and metal in the foamy vesicular-like fragments. The largest globule had a structure consisting of 40 μm Fe-Ni dendrites in a matrix of troilite. The dendrites showed typical Ni segregation, the composition at the outside being about 16 wt.% Ni with 13 wt.% Ni at the center. The troilite contained 0.1-1.5 wt.% Ni and appears to be in dis-equilibrium. A high Ni rim region was found at the troilite-dendrite interface. This region is taenite containing 29-46 wt.% Ni and about 0.3 wt.% S and was created by the rejection of Ni from the troilite. We were able to synthesize this globule; the same structure was obtained. From this simulation, the cooling rate was determined as 2.5 °C/sec. This globule probably was created by the impact of a chondrite on the moon.

A globule separated from the breccia rock apparently solidified quickly and then cooled slowly, the rock acting as a kind of crucible. This globule's metal regions contain 2 wt.% Ni, 1 wt.% P, 0.3 wt.% Co, balance Fe. There are also eutectic regions of phosphide with fine intergrowths of kamacite, troilite and carbides. This particle shows a striking similarity to spheroids from the Canyon Diablo iron. The evidence indicates that this globule was probably created by the impact of an iron meteorite on the moon.

The analysis of the metal particles makes it clear that both meteoritic and lunar Fe-FeS intergrowths are present in the