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JOURNAL OF RESEARCH of the National Bureau of Standards - A. Physics and Chemistry Vol. 75A, No. 6, November-December 1971

Publications of the National Bureau of Standards*

Selected Abstracts

Barbrow, L. E., Coordinator, U.S. Metric Study Interim Report. Department of Defense, Nat. Bur. Stand. (U.S.), Spec. Publ. 345-9, 132 pages (June 1971) $1.25, SD Catalog No. C13.10:345-9.

Key words: Department of Defense; International System of Units; metric conversion; metric system; metrication; metrication, costs and benefits of; metrication, impact of; SI; U.S. Metric Study.

This publication reports the results of a Department of Defense study, conducted pursuant to the U.S. Metric Study Act, to determine and evaluate the advantages and disadvantages, including impact on operational capability, that would attend adoption of the International System of units of weights and measures (otherwise known as the Modernized Metric System) for use in the Department (DoD). The report includes estimates for each of the major components of the DoD of the costs of a transition to metric system usage. In addition to discussing the specific advantages and disadvantages that would be expected within the Department, the report describes the dependence of the DoD on the National Industrial Base, and discusses how this interaction would be involved in a national metrication effort.

Barbrow, L. E., Coordinator, U.S. Metric Study Interim Report. The manufacturing industry, Nat. Bur. Stand. (U.S.), Spec. Publ. 345-4, 172 pages (July 1971) $1.25, SD Catalog No. C13.10: 345-4.

Key words: International System of Units; manufacturing industry; metric conversion; metric system; metric usage; metrication; metrication, attitudes toward; metrication, costs and benefits of; metrication, impact of; SI; U.S. Metric Study.

This publication reports the results of a study to assess the impacts of increasing metric usage-past, present and future-on U.S. manufacturing industry. The study, conducted pursuant to the U.S. Metric Study Act, is based on responses from more than 2,000 manufacturing companies. Information was obtained on: past and present experience with use of the metric system, including advantages and disadvantages thereof, and the views of the firms with regard to future U.S. policy - whether the country should continue its laissez faire approach to metric usage, or should undertake some sort of national program to encourage more widespread use of metric weights and measures. A separate survey of a smaller number of selected firms obtained detailed information as to estimated cost impact of a national metrication effort.

Bell, F. C., Wollin, H. F., Editors, Report of the 55th National Conference on Weights and Measures 1970, Nat. Bur. Stand. U.S.), Spec. Publ. 342, 315 pages (April 1971) $1.75. SD Catalog No. C13.6/3:342.

Key words: Conference, weights and measures-laws; weights and measures-regulations; weights and measures-technical requirements; weights and measures-history; weights and measures. This is a report of the proceedings (edited) of the Fifty-fifth National Conference on Weights and Measures, sponsored by the National Bureau of Standards, held in Salt Lake City, Utah. July 13-17, 1970, and attended by state, county, and city weights and measures officials and representatives of the Federal Government, business, industry, railroads, and associations.

Bennett, L. H., Swartzendruber, L. J., Interactions between small magnetic clusters in copper-rich Cu-Ni-Fe alloys, J. Appl. Phys. 42, No. 4, 1547-1548 (March 15, 1971).

Key words: Alloys; clustering; copper; iron; local moments; Mössbauer effect; nickel.

Traces of iron in "nonmagnetic" Cu-rich Cu-Ni alloys produce small magnetic clusters largely limited to an Fe site and its Ni nearest neighbors, as observed in Mössbauer source experiments. The present work concerns Fe Mössbauer absorber data for higher Fe concentrations (4%-3%), in the 10%-30% Ni range, which demonstrates the existence of a magnetic-moment distribution centered about two distinct moment values. For the lower Fe concentrations, the smaller and more abundant of these moments is identical to that observed in the source experiments and is associated with isolated small Fe-Ni clusters. The other moment is about twice as large and can be ascribed to coupled pairs of these small clusters. These results are almost free of effects of metallurgical clustering. By appropriate heat treatment, clustered samples are obtained with different moment distributions and higher Curie temperatures.

Brauer, G. M., Huget, E. F., Heats of immersion of the components of tooth structure, J. Dental Res. 50, No. 3, 776 (MayJune 1971).

Key words: Heats of immersion; heats of immersion of tooth structure; reactivity of anorganic whole tooth; reactivity of dentin.

Heats of immersion measurements for dentin and anorganic whole tooth powders of known specific surface were used in this study to determine quantitatively the nature and degree of surface modification produced by polar organic compounds and inorganic oxidizing agents in an aqueous environment. The experimental procedure and equipment, as well as the techniques for the preparation and physical characterization of dentin and anorganic whole tooth powders have been described elsewhere (Huget, Brauer & Loebenstein, J Dent Res 47: 291-301, 1968).

The data are compatible with previous observations that suggested preferential interaction of certain ions and functional groups with the organic matrix of dentin. The reactions occurring at the surface of dentin are similar to those exhibited by purified collagen.

Brenner. D. J.. A technique for measuring the surface temperature of transistors by means of fluorescent phosphor, Nat. Bur. Stand. (U.S.), Tech. Note 591, 49 pages (July 1971) 50 cents, SD Catalog No. C13.46:591.

Key words: Surface temperature; temperature measurement; temperature-sensitive phosphor; thermographic phosphor; transistor-chip temperature.

A technique that uses temperature-sensitive phosphor (TSP) to make quantitative measurements of transistor-chip surface temperatures over the range of 170-210 °C is described. The experimental procedure consisted of depositing a thin coating of phosphor on uncapped power transistors, and then photographing the visible fluorescence generated under near-ultraviolet (uv) excitation. The cooler regions produced a brighter fluorescence than the hotter areas. The surface temperatures of operating transistors were determined by comparing, on a point-by-point basis, the photographic density of operating photographs to the density of a family of calibration photographs. Repeated temperature measurements always fell within a 4 °C overall error range when the phosphor surface was scanned with a 25 x 25 μm aperture. The error band dropped to less than 2 °C when a 50 x 50 μm aperture was used. Coarseness of the phosphor coating seemed to limit spacial resolution to about 20 μm. Any

narrow temperature range between 20 and 400 °C can probably be measured by selecting a suitable level of uv irradiation and/or a suitable phosphor.

Cezairliyan, A., Short-time (ms) fluctuations of radiance temperature of graphite arc, Appl. Opt. 10, No. 5, 1178 (May 1971).

Key words: Graphite arc; high-speed measurements; high temperatures, pyrometry radiance standards.

Short-time fluctuations of the radiance temperature graphite arcs are investigated with a millisecond resolution photoelectric pyrometer. Standard deviation of the fluctuations around their mean is found to be 4 K. The range of low and high temperatures for four experiments extended from 3799 K to 3808 K, with an average of 3804 K on IPTS-68.

Cezairliyan, A., Morse, M. S., Beckett, C. W., Measurement of melting point and electrical resistivity (above 2,840 K) of molybdenum by a pulse heating method, (Proc. Conf. Thermophysical Properties, Manchester, England, April 7-10, 1970), Rev. Int. Hautes Tempér. Réfract t. 7, 382–388 (1970).

Key words: Electrical resistivity; high-speed; high temperatures; melting point; methods; molybdenum; properties.

A pulse heating method is used to measure the melting point and electrical resistivity of molybdenum in the temperature range 2,840 melting point in approximately 0.8 s. Specimen temperature is measured with a high-speed photoelectric pyrometer. During the heating period, voltage, current, and temperature are recorded with a highspeed digital data acquisition system which has a full-scale signal resolution of approximately one part in 8,000, and a time resolution of 0.4 ms. Results are compared with those in the literature. Estimated inaccuracy in the melting point (2,889 K) and in electrical resistivity is 10 K and 0.5 percent, respectively.

Chandler, H. H., Bowen, R. L., Paffenbarger, G. C., Development of a radiopaque denture base material, J. Biomed. Mater. Res. 5,253-265 (March 1971).

Key words: Bonding; composites; denture base materials; diagnosis; light translucency; physical properties; radiopacity.

Radiopaque glass-resin compositions were made for evaluation as denture base materials. The addition of silane-treated, radiopaque, powdered glass to clear poly(methyl methylacrylate) resulted in composites that had greater optical translucency than commercially available pink denture base resins. These formulations could be pigmented and opacified to produce materials that simulated oral soft tissues in color and translucency. Other composites were made using various monomer, polymer and glass combinations. Those made from mixes of BIS-GMA, methyl methacrylate, poly(methyl methylacrylate) and radiopaque glass had excellent translucency but handling characteristics were less ideal. Removal of very small glass particles (less than a few μm) appeared to improve optical translucency. A radiographic survey of 12 specimens that contained from 29 to 57% of the radiopaque glass indicated that all had sufficient radiopacity to aid in localization of swallowed or aspirated dentures made from such materials. Finishing procedures on composite specimens were more difficult and time-consuming and did not produce surfaces as smooth as those obtained on poly(methyl methylacrylate). The finished surfaces felt smooth to the tongue but might stain more easily in the mouth.

Chandler, H. H., Bowen, R. L., Paffenbarger, G. C., The need for radiopaque denture base materials: A review of the literature, J. Biomed. Mater. Res. 5, 245-252 (March 1971).

Key words: Denture foreign bodies; type, cause, prevention; prosthetic materials: radiopaquing agents; radiopaque denture base materials.

The need for esthetic and functionally acceptable radiopaque den

ture base materials is reflected by numerous reports of patients who ingested or aspirated portions of dentures and reports of difficul ties encountered in the removal of these dentures because they could not be located radiographically. The type of denture most commonly ingested or aspirated is a maxillary partial consisting of a palatal piece to which is attached one or more anterior teeth. It may or may not have clasps. Ingestion or aspiration of the foreign body commonly occurs with either broken or ill-fitting dentures are being worn. Few cases have been reported where patients swallowed portions of complete dentures. Previous attempts at providing radiopacity have included addition of heavy metal salts or radiopaque inserts to denture base resins. None of these attempts has been entirely successful. Elimination of dentures as foreign bodies requires a greater effort toward preventive measures by the dentist and the patient. When dentures are swallowed or inhaled, the dentist should immediately seek medical assistance for the patient. The common symptomless period following ingestion or aspiration should not lead the dentist to believe that there will not be serious subsequent complications.

Clark, R. E., Tascher, J. M., U.S. Metric Study Interim Report. Federal Government: Civilian agencies, Nat. Bur. Stand. (U.S.), Spec. Publ. 345–2, 328 pages (July 1971) $2.25, SD Catalog No. C13.10:345-2

Key words: Federal Government; International System of Units: metric conversion; metric system; metric usage; metrication; metrication, attitudes toward; metrication, costs and benefits of; metrication, impact of; SI; U.S. Metric Study.

This publication reports the findings of a survey to ascertain the views of the civilian agencies of the Federal Government on the issues raised by the U.S. Metric Study Act. With regard to internal operations of the Federal agencies, the report covers present metric (International System of Units, or SI) usage and its advantages and disadvantages, expectations of future changes in measurement usage if the U.S. continues its laissez faire policy toward the Sl. and attitudes toward a possible nationally coordinated metrication program. In the latter connection, the report contains estimates of added cost or savings impacts on agency internal operating budgets to be expected from a nominally 10-year planned metrication pres gram, both during the transition and thereafter. The survey also assessed the impacts of metric usage and of its increase on the areas of responsibility of the Federal agencies in the society al large (e.g., communications, science and technology, health, labor affairs, international affairs and trade), and on the agencies' inter faces therewith.

Devereux, C. W., Technical Standards Coordinator, Steel bi-fold closet door units, frames, and trim, Nat. Bur. Stand. (US). Prod. Stand. 38-70, 12 pages (May 1971) 15 cents, SD Catalog No. C13.20/2:38-70.

Key words: Bi-fold doors, steel; closet doors, steel bi-fold; doors, steel bi-fold; steel bi-fold doors.

This Voluntary Product Standard covers sizes, types, materials construction, hardware, and finishing of steel bi-fold closet door units and frames intended to be stock items not subject to variations according to the customer's special requirements. Methods of mark ing and labeling are included so that products which comply with the standard may be clearly identified. Provisions for the erection f doors, frames, and accessories are not included in the standard. but certain recommendations for storage and erection as generally endorsed by the manufacturers are given for information and guidance.

Domalski, E. S., Thermochemical properties of peroxyacetyl (PAN) and peroxybenzoyl nitrate (PBN), Environ. Sci. Tech Communications 5, 443–444 (1971).

Key words: Bond additivity method; group additivity method. peroxyacetyl nitrate; peroxybenzoyl nitrate; thermochemica properties.

The thermochemical properties of peroxyacetyl nitrate (PAN) an peroxybenzoyl nitrate (PBN) were estimated by means of bond are group additivity schemes. Values are given at 298.15 K for the follow

ing properties: AHƒ° (g), Cp° (g), S° (g), Cp° (liq), AHvap, and AH sublim.; these values were used to calculate ASƒ° (g), AGƒ° (g), Cp° [(liq)-(g)], AHƒ° (liq), and AHƒ° (s), which are also cited.

Eisele, J. W., Technical Standards Coordinator, School Chalk, Nat. Bur. Stand. (U.S.), Prod. Stand. 30-70, 14 pages (May 1971) 15 cents, SD Catalog No. C13.20/2:30–70.

Key words: Calcium carbonate; calcium sulfate; chalk; chroma; toxicity; whiting.

This standard provides requirements for the dimensions, material, breaking strength, characteristics, toxicity, workmanship, and chroma (as applicable) for six types and several classes and grades of school chalk. Test methods for determining the material content, breaking strength, and chroma are provided. Standard packages are given, and methods for labeling to indicate compliance with the Standard are provided.

Evenson, K. M., Radford, H. E., Moran, M. M., Jr., CH free radicals detected by infrared laser magnetic resonance, Appl. Phys. Letters 18, No. 10, 426–429 (May 15, 1971).

Key words: CH; far infrared; free radical; laser; laser magnetic

resonance.

CH radicals in an oxyacetylene flame have been detected by a magnetic resonance absorption method, with a water-vapor laser as the source oscillator at a frequency of 2.5 THz. The absorption spectrum s identified with the pure rotational transition, J, K=(5/2, 2)→ (7/2, 3) at a wavelength of 118.6 μm.

ong, E., A preliminary design of a date retrieval language to andle a generalized data base: DRL, Nat. Bur. Stand. (U.S.), ech. Note 590, 26 pages (July 1971) 35 cents, SD Catalog No. 13.46:590.

Key words: Data base; data retrieval; data structure; information torage and retrieval; language extension; preprocessor; programing language.

RL (Data Retrieval Language) is a high-level programming language or information retrieval. The language includes a data description Inguage which can describe fixed-length hierarchical data strucires, and DRL includes a data retrieval statement whereby a user an retrieve data by specifying conditions on to the data value. DRL so has an environment declaration statement in which the user can dicate specific peripheral devices by unit number for files. The st of the language consists of an operation repertory of inputitput functions and other data manipulations.

RL is implemented as a preprocessor to FORTRAN V on the NIVAC 1108, under EXEC II Operating system. Key words act triggers and are replaced by blocks of FORTRAN code.

he purpose of this project is to investigate the design of an informaon retrieval language to handle a generalized data base. The DRL 'stem consists of a set of primitives utilizing both compile-time acros and runtime subroutines. These primitives are embedded in high-level procedure-oriented programming language—the “host nguage" - FORTRAN in this case. These primitives form a base on which a class of languages can be defined.

ranklin, A. D., Marzullo, S., 9.- EPR study of point-defect quilibria in CaF2 containing GdF3, Proc. No. 19 British Cernic Society, "Role of Point Defects in Solid State Mass", Mass ansport Proc. Non-Metallic Solids, London, England, Dec. 17-18, 69, pp. 135-150 (British Ceramic Society, Stoke-on-Trent, England,

71).

ey words: Calcium fluoride; defect equilibria; electron paraagnetic resonance; point defects.

om temperature measurements have been made of EPR spectra 9.5 GHz arising from tetragonal and cubic centers in CaF2 conining GdF3. The concentrations ranged from 0.01 to 0.45 mol %. e crystals were annealed in a 30:1 He-HF atmosphere at temperres ranging from 500 to 1100 °C and then rapidly cooled to room nperature. The annealing times were long enough to achieve ady-state EPR data, and the cooling rapid enough so that a

considerably slower cooling gave essentially the same result. It was found that the ratio of the concentration of tetragonal centers to that of cubic centers diminished as the total GdF concentration increased. At a given GdF3 concentration, this ratio passed over a maximum as the annealing temperature increased. This behavior is inconsistent with a model including only anion interstitials and vacancies. If cation vacancies are included, and if they are assumed to be immobile while the anions can move during cooling, the quali tative features of the data can be produced by the model. Direct experimental confirmation of these assumptions and of the presence of cation vacancies has not been obtained.

Geist, J. C.. Richmond, J. C., On the absorptance of cavity-type receivers, Nat. Bur. Stand. (U.S.), Tech. Note 575, 38 pages (July 1971) 45 cents, SD Catalog No. C13.46:575.

Key words: Absorptance; black coatings; cavity absorptance; cavity reflectance; laser-source reflectometer; Parsons black; retro-reflectance.

The directional-hemispherical reflectance of a number of flat samples that had been coated with Parsons Optical Black Lacquer procured from Thos. Parsons and Sons and The Eppley Laboratory, respectively, was measured at 0.6328 and 1.15 μm with a laser-source integrating sphere reflectometer. The reflectance varied significantly with method of application, and was significantly higher for the Eppley lacquer than for the Parsons lacquer. The reflectance of two cavity receivers, one coated with each lacquer, was also measured. At 0.6328 μm the reflectance of the Parsons cavity was higher, but at 1.15 μm it was lower. The measured reflectance of the Parsons cavity was appreciably higher than that computed from the measured reflectance of the lacquer and the geometry of the cavity, assuming the coating to be a perfectly diffuse reflector. Retro-reflectance measurements revealed that both lacquers reflected more radiant energy back into directions near the direction of incidence than would a perfect diffuser of the same directionalhemispherical reflectance, but the Parsons lacquer was by far the more pronounced retro-reflector. The principal conclusion is that the diffuse assumption can lead to significant errors in computing the absorptance of cavity-type receivers, when the cavity coating is in fact not diffuse.

Geller, S. B., Standard reference materials: Calibration of NBS secondary standard magnetic tape (computer amplitude reference) SRM 3200 using the reference tape amplitude measurement "Process A" Model II, Nat. Bur. Stand. (U.S.), Spec. Publ. 260-29, 57 pages (June 1971) 60 cents, SD Catalog No. C13.10:260–29.

Key words: Average signal peak level; computer amplitude refer ence; magnetic tape; master standard; saturation curves; secondary standard: signal level calibration; standard reference materials; unrecorded reference.

This publication describes the design, operation and calibration of the NBS signal amplitude measuring system (Process A- Model II) that is used for calibrating unrecorded Secondary Standard Magnetic Tapes (Computer Amplitude Reference) SRM 3200. This system supercedes the measurement system that was described in the NBS Special Publication 260-18 (November 1969). The signal level calibration is made with respect to a reference signal level derived from the NBS Master Standard Magnetic Tape (Computer Amplitude Reference) that is kept in repository at NBS. The techniques for measuring and recording the data that accompany each Secondary Standard Magnetic Tape in the form of strip chart recordings and saturation curves are described.

Godfrey, J. T., Vidal, C. R., Smith, E. W., Cooper, J., Effect of time ordering in the unified theory, Phys. Rev. A. 3, No. 5, 1543-1546 (May 1971).

Key words: Lyman-a; Stark-broadening; time-ordering; unified theory.

Using a previously developed unified theory of spectral line broadening, the effects of time-ordering over the complete line profile are investigated. The results of calculations for the Lymanalpha line are presented.

443-082 OL 71-6

Godfrey, J. T., Vidal, C. R., Smith, E. W., Cooper, J., The effect of time ordering on the Lyman a profile, Nat. Bur. Stand. (U.S.), Monogr. 121, 14 pages (June 1971) 30 cents, SD Catalog No. C13.44:121.

Key words: Lyman-a; Stark-broadening; time-ordering; unified theory.

Using a unified theory of spectral line broadening previously developed, the effects of time-ordering over the complete line profile are investigated. The behavior of the time-ordered thermal average and un-time-ordered thermal average is obtained analytically. Calculations for the line profile of the Lyman-a line of hydrogen are presented and are representative in that the full thermal average is replaced by the thermal average with the electron velocity distribution approximated by f(v) = d(v-vay) where vay is the thermal velocity for the plasma in question.

Haller, W., Simmons, J. H., Napolitano, A., Viscosity-drift technique for determination of critical liquid-liquid immiscibility temperature of glasses, J. Am. Ceram. Soc. 54, No. 6, 299-302 (1971).

Key words: Glass, viscosity; immiscibility; phase-separation; viscosity-drift.

The time dependence of the low-temperature viscosity was used to determine the occurrence of phase separation in glass systems and to measure the critical immiscibility temperature. The technique is fast and easily performed and can be applied to materials with very low immiscibility gaps. Immiscibility temperatures for several technically important glass compositions are given.

Haller, W., Winogradoff, N. N., Explosive vapor release as cause of laser-induced surface damage of glass, J. Am. Ceram. Soc. 54, No. 6, 314–315 (1971).

Key words: Glass; laser; laser-energy; laser-damage.

Exposure of polished glass surfaces to focused gigawatt laser pulses causes roughening of the illuminated area and emission of small glass fragments (sputtering). Since the formation of the lesion obviously relates to the amount of energy absorbed, glass targets with various degrees of optical absorption for the laser light were studied. Three optical filter glasses of known absorption were exposed to single, nominal 30-J pulses of a 30-ns Q-switched Nd glass laser. The filter glasses were BG 18, KG3, and NG 1; the BG 18 has the strongest absorption for the laser wavelength.

Hatos, S. L., U.S. Metric Study Interim Report. Commerical weights and measures, Nat. Bur. Stand. (U.S.), Spec. Publ. 345-3, 116 pages, (July 1971) $1.00, SD Catalog No. C13.10:345-3. Key words: Commercial weights and measures, International System of Units; metric conversion; metric system; metric usage; metrication; metrication, attitudes toward; metrication, costs and benefits of; metrication, impact of; SI; U.S. Metric Study.

This publication, one of a series prepared pursuant to the U.S. Metric Study Act, explores the impacts metrication would have on commercial weights and measures activities. More specifically, the report, concerns: (1) the cost of adapting or changing commercial weighing and measuring devices to record and/or indicate in metric units. and (2) the effects of metrication on state and local weights and measures jurisdictions.

Haupt, G. W., Glass limit standards deposited at NBS for railway, highway and airways traffic signal colors-history, permanence and colorimetric properties, Nat. Bur. Stand. (U.S.). Tech. Note 564, 121 pages (June 1971) $1.00, SD Catalog No. C13.46:564.

Key words: Aircraft signals; color standards: filter permanence; limit filters; railroad signals; signal colors; signal standards; spectral transmittance of glass filters; traffic signals.

Signal glass limit standards for railway, highway, and aviation colors, selected by user-organizations, are on deposit at the National

Bureau of Standards. Many duplicates of these standards have been issued by NBS.

The first standards were selected in 1931 for railway use. Highway standards were adopted in 1940, and selection of aviation standards began in 1942. At the present time the NBS is custodian of 63 standards for these signal colors.

Permanence of the filters is examined, based on colorimetric con versions for CIE standard illuminant A derived from spectrophoto metric measurements made on different instruments over periods of years.

Spectral transmittance data and the resulting colorimetric data are given for 9 illuminants ranging in distribution temperature from 1500 to 3250 kelvins and for CIE standard illuminants B and C. Figures show, for several filters of each color, the shifts occurring both in chromaticity (x, y) and in redness and brightness index (u, W*) with changes in illuminant.

Hoeve. C. A. J., On the general theory of polymer absorption at a surface. J. Polymer Sci. Symposia, Part C, No. 30, 361–36° (1970).

Key words: Configurations; excluded volume effect; loops; polymer adsorption; surface layer; point; trains.

Previous theoretical work dealt with polymer absorption in which, the adsorbed segments (trains) interact in the surface laver only In this work the treatment is extended to include also interaction between the loops dangling in solution. Fortunately, the excluded volume effects for adsorbed polymer chains are found to be smau Therefore an approximate treatment is possible that leads to equations that govern polymer chains under a wide variety of conditions.

Hudson, R. D., Kieffer, L. J., Compilation of atomic ultraviolet photoabsorption cross sections for wavelengths between 3000 and 10 Å, Atomic Data 2, No. 3, 205–262 (May 1971).

Key words: Atoms; compilation; cross section data; photoabsorption: photoionization; photon.

Graphical displays of selected experimental data on atomic photi absorption cross sections as functions of wavelength are presented for 24 atoms. Criteria used in the data selection are discussed References for all data chosen and an author index are included The literature has been covered through October 1969.

Hummer, D. G., Rybicki, G. B., Radiative transfer in spherically symmetric systems. The conservative grey case, Monthus Notices Roy Astron. Soc. 152, No. 1, 1–19 (1971).

Key words: Eddington factor; model atmospheres; spherical radiative transfer.

A practical computational method is presented for the solution of radiative transfer problems in spherically symmetric systems This procedure involves iteration on the "Eddington factor"ƒ=K! and is designed to handle the forward peaking of the radiation head in extended spherical systems. Extensive numerical results are obtained and discussed for systems in which кp=r ", 0 < r < R. 1»t n=3/2, 2 and 3.

Jacox, M. E., Milligan, D. E., Matrix-isolation study of the vacuum-ultraviolet photolysis of chloroform. Infrared spectra of the CC, HCCI, and HCCI molecular ions. J. Chem. Phys. 54, No. 9, 3935–3950 (May 1, 1971).

Key words: CCl; chloroform; electron attachment; HCCI,. HOC' HCC13; infrared spectrum; matrix isolation; photoionization; vacu!= ultraviolet photolysis.

Photolysis of samples of HCCl, isolated in an argon matrix at 14 K using 1216-A radiation leads not only to the isolation of a high vir d of CCl3, but also to the photoionization of CC, resulting in the stabilization of a sufficient concentration of CCl; for direct infrared spectroscopic identification. The assignment of still other intrar-d

bsorptions which appear in this system to negatively charged pecies has been confirmed by experiments in which a small conentration of an alkali metal atom is also present in the matrix, roviding a photoelectron source. When matrix-isolated HCCl3 subjected to photolysis by 1067-A argon resonance radiation, ery little CC3 is produced, but HCCl2, HCC, and the same egatively charged species are stabilized in significant concentration. tudies of chloroform samples enriched in carbon-13 and of DCC13 amples have provided support for these identifications and have ielded data necessary for obtaining several of the force constants f these species. The infrared spectrum of the negatively charged pecies can most satisfactorily be explained by postulating that issociative electron attachment to chloroform occurs, resulting the stabilization of HCCl in the matrix environment.

ennings, D. A., Baldwin, D. L., Construction of a flashlampumped dye laser and an acousto-optic modulator for ode-locking, Nat. Bur. Stand. (U.S.), Tech. Note 603, 33 pages July 1971) $1.00, SD Catalog No. C13.46:603.

ey words: Acousto-optic modulator: flashlamp-pumped dye laser; ode-locking; subnanosecond pulses.

1 this paper is presented the design of a flashlamp-pumped dye ser capable of emitting light pulses 500 ns wide (FWHM) with a setime of 300 ns. The energy output in the visible region of light is to 10mJ with an energy conversion efficiency of about 0.01% at a epetition rate of 30 pps. The design of an acousto-optic modulator sed to mode-lock the dye laser by intracavity loss modulation is resented. The laser output for a given cavity length depends on the requency and voltage applied to the modulator; a 10%-100% nodulated output can be obtained with 1 V rms-20 V rms, whereas train of light pulses narrower than 0.8 ns (FWHM) can be obtained with 80 V rms.

Jein, M., Practical treatment of coupled gas equilibrium, Chapter in Physical Chemistry, Vol. 1, Thermodynamics, Chapter 7, 89-544 (Academic Press, Inc., New York, N.Y., 1971).

Key words: Chemical equilibrium; chemical reactions; equilibrium; (ases; mass action; non-linear search.

Equations are derived for the species concentrations in coupled hemical equilibria in the gas phase. This is done both for the method of the direct minimization of the free energy as well as for the equilibrium constant method. The relations developed are such as to allow for the inclusion of detailed real gas effects. The emphasis is on practical problems encountered in the actual calculation of the species and the thermodynamic properties. Expressions are derived for the direct calculation of the concentration derivatives with respect to temperature and density required for the calculation of the derived properties (i.e. specific heats, sound velocities, etc.). Considerable space is given to discussions of the non-linear numerical methods available for the solution of the non-linear equations for the species concentrations.

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are presented in comparison with experimental results of other workers.

Kurylo, M. J., Peterson, N. C., Braun, W., Temperature and pressure effects in the addition of H atoms to propylene, J. Chem. Phys. 54, No. 11, 4662-4666 (June 1, 1971).

Key words: Absolute rate constant; activation energy; fluorescence; H atom; propylene; reaction kinetics.

The effect of He pressure on the rate of addition of hydrogen atoms to propylene was measured at 298 K. H atom signal was recorded by the method of resonance of Lyman a radiation at 121.6 nm. The results are consistent with the 1/p dependence of ki recently observed in the H atom-ethylene system. The limiting high pressure rate constant obtained in this work is

H+C3H6→C3H7k1 = 1.61±0.04 × 10-12 cm3molec-'s-1.

The temperature dependence of the H atom addition was investigated at 50 torr total pressure over the temperature range 177-473 K. Analysis of the data below room temperature gives the following Arrhenius parameters for addition to the terminal olefinic position: kg (10.18±0.26) × 1012 exp [−(1211±11)/1.98T] cm3molec-'s-1 Deviations from this dependence above 298 K can be assigned to non-terminal addition. H atom abstraction, and increased decomposi tion of the excited propyl radicals.

Linsky, J. L., Can the Ion H+ account for missing opacity in the solar ultraviolet? Solar Physics 11, No. 2, 198–207 (February 1970).

Key words: H1; opacity, continuous; solar photosphere; solar ultraviolet spectrum.

Limb darkening and specific intensity data imply more continuous opacity in the solar photosphere between 2000 Å and 3500 Å than has been predicted theoretically. The temperature dependence and wavelength dependence of this missing opacity are in qualitative agreement with those deduced for the ion H, but it is unlikely that Hy is sufficiently abundant to account for this opacity.

Linsky, J. L., On the relative residual intensities of the calcium H and K lines, Solid Physics 11, No. 3, 355–373 (March 1970).

Key words: Non-LTE radiative transfer; resonance lines, Ca II; solar chromosphere, physical properties; solar chromosphere, structure; spectral line formation; spectroscopic diagnostics.

We have observed the solar Ca II H and K lines to obtain well-calibrated ratios of their core residual intensities. From three independent calibrations, one using a standard lamp, we conclude that the residual intensity ratio r(K3)/r (H) is 1.048±0.03 in the quiet chromosphere and 1.20±0.03 in a plage region. These ratios correspond closely to those observed in stars with quiet and active chromospheres, respectively. For a chromospheric model suggested by the calcium lines and a four-level Ca II ion, we compute H and K line profiles varying the direct collisional coupling and indirect radiative and collisional coupling via the 3 D level. We conclude that enhanced chromospheric activity in the sun and late-type stars results more from a steepening of the chromospheric thermal gradient than from a change in density.

Linsky, J. L., Teske, R. G., Wilkinson, C. W., Observations of the infrared triplet of singly ionized calcium, Solar Physics 11, No. 3, 374-383 (March 1970).

Key words: Non-LTE radiative transfer: resonance lines, Ca II; solar chromosphere, physical properties; spectral line formation; spectroscopic diagnostics.

Observations are presented of the Ca II infrared triplet (8498 Á, 8542 A, and 8662 A) at three positions on the solar disk to make possible direct analyses of the line and comparisons with theoretical

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