Monogr. 120. Unified theory calculations of Stark broadened hydrogen lines including lower state interactions, C. R. Vidal, J. Cooper, and E. W. Smith, Nat. Bur. Stand. (U.S.), Monogr. 120, 45 pages (Jan. 1971).

Key words: Classical path; hydrogen lines; line wings; Stark broadening; unified theory.

Recently published calculations of hydrogen Stark broadening on the basis of the unified classical path theory have been extended to include lower state interactions in the final line profile. A detailed comparison with experiments in the density range 1013-107 cm3 is given

Monogr. 121. The effect of time ordering on the Lyman a profile, J. T. Godfrey, C. R. Vidal, E. W. Smith, and J. Cooper, Nat. Bur. Stand. (U.S.), Monogr. 121, 14 pages (June 1971).

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 are compared. The Fourier transform of the 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 ƒ(v)=dv—vav) where vay is the thermal velocity for the plasma in question.

Monogr. 122. Mechanics of pneumatic tires, S. K. Clark, Editor, Nat. Bur. Stand. (U.S.), Monogr. 122, 853 pages (Nov. 1971). Key words: Friction; rubber; skid; tire contact; tire cord; tires; tire stress; tire structure; vehicles.

The pneumatic tire has been an integral part of automotive transportation almost since its inception, yet it remains a product whose characteristics are not easily predictable or comprehensible by conventional engineering techniques. This treatise is an attempt to provide a rational descriptive and analytical basis for tire mechanics. Chapters of this book are contributed by active research workers in the fields of rubber and textile properties, friction, material properties, tire stress problems, tire design and construction, vehicle skid and handling, and tire mechanical properties.

Monogr. 123. BOLOVAC systems for measuring electrical quantities from 0.5 MHz through microwaves, M. C. Selby, Nat. Bur. Stand. (U.S.), Monogr. 123, 24 pages (Jan. 1972).

Key words: BOLOVAC; calibration of current meters through microwaves; calibration of power meters through microwaves; calibration of voltmeters through microwaves; current measurement; disk-type bolometer evaluation; frequency-domain pulse evaluation; measurement of microwave current; measurement of microwave power; measurement of microwave voltage; mismatch error; picosecond rise-time pulse evaluation; power measurement; pulse-rise-time standardization; sampling oscilloscope standardization; spectrum analyzer standardization; termination mismatch error elimination; thin-film bolometers; voltage measurement.

A novel device-the BOLOVAC-is employed in measurement systems that furnish known voltages and currents up to 18 GHz, remove serious difficulties in power measurements, and are applicable in impedance, attenuation and other measurements. Typical of such measurements are the evaluation of rf power sources; calibration of power meters; measurement of net and incident power flow in a system; calibration of signal genera

tors, voltmeters, current meters, picosecond-rise-time pulse-display oscilloscopes, spectrum analyzers; determination of insertion loss of components; and calibration of directional couplers. The Bolovac also serves as an accurately known resistive termination for match or mismatch applications from LF through microwaves.

Monogr. 124. Reference tables for low-temperature thermocouples, L. L. Sparks, R. L. Powell, and W. J. Hall, Nat. Bur. Stand. (U.S.), Monogr. 124, 61 pages (June 1972).

Key words: Cryogenics; homogeneity tests; liquid helium; liquid hydrogen; liquid nitrogen; thermocouples.

The experimental program to establish low-temperature reference tables for the commonly used thermocouples has been completed. Details of the experimental system, instrumentation, data analysis, error analysis, and materials tested are given in order to allow the user to better evaluate and apply the results. The results presented here include: (1) Reference tables for thermocouple types E, K, and T, both as E=f(T) and T=ƒ(E). The shorter f(E) tables have a 0 °C (273.15 K) reference temperature while all other tables have a 0 K reference temperature; (2) Reference tables for Pt and Ag-28 at% Au vs the materials used in thermocouple types E, K, and T. These data are presented as E=f(T) only; (3) Orthogonal polynomials and the associated coefficients necessary to generate the data with reduced order approximations; and (4) Power series coefficients for full precision reproduction of the reference data.

The data presented in the E=f(T) tables cover the temperature range from 0 to 280 K. The T=f(E) tables cover temperature ranges from 273.15 K down to the lowest temperatures allowed by table resolution.

Monogr. 125. Thermocouple reference tables based on the IPTS68, R. L. Powell, W. J. Hall, C. H. Hyink, Jr., L. L. Sparks, G. W. Burns, M. G. Scroger, and H. H. Plumb, Nat. Bur. Stand. (U.S.), Monogr. 125, 410 pages (Mar. 1974) SD Catalog No. C13.44:125.

Key words: base metal alloys; noble metal alloys; temperature scale; temperature standards; thermocouples; thermometry.

Revision of the International Practical Temperature Scale requires that there be changes for all accurately tabulated thermophysical values. Revised reference data for thermocouples have been generated in a cooperative program between groups of the National Bureau of Standards in Boulder and Gaithersburg. This Monograph contains tables, analytic expressions, various approximations, and explanatory text. Only the standard letter-designated thermocouples are described: noble metal Types S, R, and B and base metal Types E, J, K, and T. Their appropriate "single-leg" or thermoelement versus Pt-67 values are also included. The new reference data reflect not only revisions in the temperature scale, but also slight changes in the materials themselves and improvements in data fitting methods. The temperature ranges vary for different types, from a low of - 270 °C for Type E to a high of 1820 °C for Type B. The main functions and tables are given in terms of Celsius degrees and microvolts. Tables in the appendices represent the data with less precision, in millivolts, and in degrees Fahrenheit as well as Celsius. Approximate quadratic, cubic, and quartic analytic expressions are also given for each thermocouple type in various temperature ranges. Supersedes NBS Circular 561.

Monogr. 125, Suppl. 1. Thermocouple reference tables based on the IPTS-68: Reference tables in degrees Fahrenheit for thermoelements versus platinum (Pt-67), R. L. Powell and G. W. Burns, Nat. Bur. Stand. (U.S.), Monogr. 125, Suppl. 1, 46 pages (Jan. 1975) SD Catalog No. C13.44:125/Suppl. 1.

Key words: base metals alloys; noble metal alloys; temperature scale; temperature standards; thermoelements; thermometry.

Reference tables for several thermoelements versus platinum (Pt-67) are given with values of the thermoelectric voltage as a function of temperature in degrees Fahrenheit. Only tables for standard letter-designated thermoelements are included: Types BP, BN, JP, JN, KP (same as EP), KN, TP, and TN (same as EN). These tables supplement those given in NBS Monograph 125 and were calculated from the power series expansions presented in that Monograph. They are based upon the absolute electrical units and the International Practical Temperature Scale of 1968 (IPTS-68).

Monogr. 126. Platinum resistance thermometry, J. L. Riddle, G.
T. Furukawa, and H. H. Plumb, Nat. Bur. Stand. (U.S.),
Monogr. 126, 129 pages (Apr. 1973) $2.10, SD Catalog No.
C13.44:126.

Key words: Calibration; calibration errors; cryostat; fixed
points; freezing point; International Practical Temperature
Scale; platinum resistance thermometer; Thermodynamic
Temperature Scale; thermometry; triple point.

The monograph describes the methods and equipment employed at the National Bureau of Standards for calibrating standard platinum resistance thermometers (SPRT) on the International Practical Temperature Scale (IPTS-68). The official text of the scale is clarified and characteristics of the scale are described. Several designs of SPRT's are shown and discussed in the light of the requirements and recommendations on the text of the IPTS-68. Possible sources of error such as those due to the internal and external self-heating effects and the immersion characteristics of SPRT's are described in detail. Precautions and limitations for the mechanical and thermal treatment and for the shipment of SPRT's are indicated, and a guide is given for those desiring the thermometer calibration services of NBS. The description of equipment employed at the National Bureau of Standards for maintaining the IPTS-68 includes the triple point of water cell, tin point cell, zinc point cell, oxygen normal boiling point comparison cryostat, the 13 to 90 K comparison cryostat, and the reference SPRT's upon which the NBS- IPTS-68 in the region 13 to 90 K is based. Methods are given for calculating temperatures from the calibration data and observed resistances; the propagation of calibration errors is discussed. Supplemental information given in the Appendixes includes the authorized English version of the text of the IPTS-68, tabular values of the "reference function" used below 0 °C, tabular values of the differences between IPTS-68 and IPTS-48, analysis of the first derivatives at 0 °C of the IPTS-68 formulations, methods for calibrating potentiometers and Mueller bridges, and the derivation of the coefficients used in the analysis of error propagation. Monogr. 127. NBS papers on underground corrosion of steel piling 1962-1971. Corrosion of steel pilings in soils, corrosion evaluation of steel test piles exposed to permafrost soils, performance of steel pilings in soils, and polarization measurements as related to corrosion of underground steel piling, W. J. Schwerdtfeger and M. Romanoff, Nat. Bur. Stand. (U.S.), Monogr. 127, 63 pages (Mar. 1972).

Key words: Active region; aerated soil; corrosion; disturbed soil; excavated; extracted; H-piling; instantaneous corrosion rate; mill scale; permafrost region; pipe piling; pit depth; polarization; sheet piling; undisturbed soil; weight loss.

This monograph is a collection of published papers on underground corrosion of steel piling. The papers are as follows: (1) Romanoff, Melvin, Corrosion of Steel Pilings in Soils, Nat. Bur.

Stand. (U.S.), Monogr. 58, (Oct. 1962); (2) Romanoff, Melvin, Corrosion Evaluation of Steel Test Piles Exposed to Permafrost Soils, Proceedings 25th Conference, National Association of Corrosion Engineers, page 6 (Mar. 1969); (3) Romanoff, Melvin, Performance of Steel Pilings in Soils, Proceedings 25th Conference, National Association of Corrosion Engineers, page 14 (Mar. 1969); (4) Schwerdtfeger, W. J., Polarization Measurements as Related to Corrosion of Underground Steel Piling, J. Res. Nat. Bur. Stand. (U.S.), 75C (Eng. and Instr.) No. 2, 107121 (Apr.-June 1971).

The papers describe corrosion of various types of steel piling exposed underground in the United States under climatic conditions ranging from semi-tropical to frigid. Corrosion is described on driven piling above and below the water table after many years of exposure in soils having resistivities between 78 and 50,000 ohm-cm and ranging in pH from 2.3 to 8.8.

One of the papers demonstrates the value of a polarization technique in measuring corrosion. Polarization data were obtained on weighed steel pipe specimens exposed underground for seven years in backfilled soil trenches in the vicinity of driven sheet piling. The technique was evaluated by comparing calculated cumulative weight losses of specimens with their actual weight losses. The technique was also shown to be applicable to underground pipe piling. Supersedes NBS Monograph 58.

Monogr. 128. Corrosion rates on underground steel test piles at Turcot Yard, Montreal, Canada- Part 1, W. J. Schwerdtfeger and M. Romanoff, Nat. Bur. Stand. (U.S.), Monogr. 128, 17 pages (July 1972).

Key words: Average penetration rate; H-piles; instantaneous corrosion rate; linear polarization; pit depth; polarization curve.

In 1966, isolated steel H-piles allocated for underground corrosion tests were installed in three locations at the Turcot Yard Interchange of the Transcanadian Highway at Montreal. The reason for the installation was to furnish answers to some questions concerning the corrosion characteristics of piles, 12 in74 lb/ft(30.5 cm-110 kg/m), which are identical with the piles supporting the concrete piers under the highway. Polarization measurements have been made once every year since installa

tion.

This paper describes the determination of corrosion rates based on the polarization measurements made up to the time of removal of the first group of piles in 1969. The piles, placed underground at the three locations, differ mainly in that at one site all the piles are bare, at the second site the upper ends of the piles are coated with an epoxy paint and at the third site the upper ends are encased in concrete. Physical measurements made on the cleaned piles after removal are correlated with corrosion rates calculated from the polarization measurements. Also, penetration rates on the piling based on the polarization data are compared with average penetration rates (based on actual weight losses) on relatively small pipe specimens. The pipe specimens were removed from 28 underground sites having a range of soil resistivities comparable to those of the three piling sites.

Using one of the polarization techniques applied to the individual test piles, polarization measurements were also carried out on 32 interconnected piles supporting one of the concrete piers. The calculated average corrosion rate of the 32 piles was found to compare favorably with that of the separate test piles in the same area.

Monogr. 129. The development of Loran-C navigation and timing, G. Hefley, Nat. Bur. Stand. (U.S.), Monogr. 129, 144 pages (Oct. 1972).

Key words: Cyclan; cytac; Loran; Loran-C; low frequency; navigation; pulse propagation; radio positioning; time dissemination; time transfer system.

The Loran-C timing and navigation concept and its implementation in the form of the Loran-C system has taken on considerable importance in a variety of military and civilian applications such as microsecond clock synchronization, precision tactical or civil navigation, etc. Future applications like tying together continental surveys, aircraft collision avoidance, etc., have yet to be explored in detail. This work traces the development of the Loran-C concept from its inception as a 100 kHz pulse hyperbolic navigation system to more recent times when it found a variety of applications to both timing and navigation. This work is intended to present the story of Loran-C in a readable and understandable way without resorting to the complicated mathematical formulation of the theory or detailed instrumentation aspects. Thus, the history, experimental and theoretical developments, political decisions, and field testing of the early equipment are described and the lessons learned can certainly be a guide for modern development of the system in all its detailed applications.

Monogr. 130. The divergent beam (Kossel) x-ray method and its uses in measuring strain contours in an individual grain of Fe-3 weight percent Si transformer sheet, H. Yakowitz, Nat. Bur. Stand. (U.S.), Monogr. 130, 80 pages (Aug. 1973) 95 cents, SD Catalog No. C13.44:130.

Key words: Divergent beam x-ray diffraction; electron probe microanalysis; iron-silicon alloy; Kossel; strain; stress; transformer sheet.

Residual and impressed stresses and strains in Fe-3 wt. pct. Si alloy transformer sheet were studied. Results were obtained by the divergent beam (Kossel) x-ray microdiffraction techniques. The optically opaque Fe-3 wt. pct. Si alloy was mapped for residual and impressed stresses and strains. These maps are roughly analogous to polarized light stress analysis of transparent materials. The results showed that a variable strain distribution existed in the alloy sheet at the time it was ready for insertion into a transformer core. Small applied compressive and tensile loads tended to rearrange this variable strain distribution but not to appreciably alter the total stored elastic energy. Monogr. 131. Thermal conductivity of solids at room temperature

and below. A review and compilation of the literature, G. E. Childs, L. J. Ericks, and R. L. Powell, Nat. Bur. Stand. (U.S.), Monogr. 131, 624 pages (Sept. 1973) $7.80, SD Catalog No. C13.44:131.

Key words: Cryogenic thermal conductivity; elements, alloys, commercial metals, semiconductors, semimetals, ionic and valence crystals, minerals, molecular crystals, polymers, glasses, disordered dielectrics, thermal conductivity of; review; thermal conductivity.

An extensive compilation is given of the measured values of thermal conductivity for nearly all solid materials from room temperature down to 0.01 kelvin. The reviewed materials include elements, alloys and commercial metals, semiconductors, semimetals, ionic and valence crystals, minerals, molecular crystals, polymers, glasses, and disordered dielectrics. Excluded are foams, powders, earths, fibers, layers of composites, and similar other heterogeneous solids. Data for temperatures below 1 kelvin are presented separately. The tables and graphs are complete for literature references from 1900 to mid-1971. Experimental methods and physical phenomena are discussed in the text and coded in the tables for references for which curves are shown. Supersedes NBS Circular 556.

Monogr. 132. A compilation and evaluation of mechanical, thermal, and electrical properties of selected polymers, R. E. Schramm, A. F. Clark, and R. P. Reed, Nat. Bur. Stand. (U.S.), Monogr. 132, 848 pages (Sept. 1973) $10.25, SD Catalog No. C13.44:132.

Key words: Compilation; electrical properties; mechanical properties; plastics; polymers; thermal properties.

This compilation abstracts original experimental data on the mechanical, thermal, and electrical properties of six commercially available polymers. After an extensive review of the open literature, all available data were collected together in graphical and tabular form along with material characterization, experimental method, and reference to the original publication. The data are also summarized and a brief description of each polymer is included.

Monogr. 133. Mass and mass values, P. E. Pontius, Nat. Bur. Stand. (U.S.), Monogr. 133, 39 pages (Jan. 1974) SD Catalog No. C13.44:133.

Key words: apparent mass; buoyancy corrections; mass comparison; mass value; true mass; weighing.

There are several bases for assigning mass values to weights to be used as mass standards. As a consequence a given weight may have several assigned mass values depending on the basis used. In many cases, the differences between these assigned values, although easily detectable with precise weighing equipment, are of no practical concern. However, in some instances these differences may be crucial. The first part of this paper is a historical summary of weighing, standards, and the assignment of value; and the interfacing of mass measurements with civilization. The second part of this paper discusses in detail the methods of assigning mass values. Ways to convert from values on one basis to values on another basis are discussed. Sample problems relating to the buoyant effect of the air are presented in the appendices.

Monogr. 134. Space groups and lattice complexes, W. Fisher, H. Burzlaff, E. Hellner, and J. D. H. Donnay, Nat. Bur. Stand. (U.S.), Monogr. 134, 184 pages (May 1973) $4.10, SD Catalog No. C13.44:134.

Key words: Crystallography; crystal point groups; crystal structure; lattice complexes; site sets; space groups.

The lattice complex is to the space group what the site set is to the point group- an assemblage of symmetry-related equivalent points. The symbolism introduced by Carl Hermann has been revised and extended. A total of 402 lattice complexes are derived from 67 Weissenberg complexes. The Tables list site sets and lattice complexes in standard and alternate representations. They answer the following questions: What are the coordinates of the points in a given lattice complex? In which space groups can a given lattice complex occur? What are the lattice complexes that can occur in a given space group? The higher the symmetry of the crystal structures is, the more useful the latticecomplex approach should be on the road to the ultimate goal of their classification.

Monogr. 135. Properties of glasses in some ternary systems containing BaO and SiO2, G. W. Cleek and C. L. Babcock, Nat. Bur. Stand. (U.S.), Monogr. 135, 42 pages (Sept. 1973) 70 cents, SD Catalog No. C13.44:135.

Key words: Barium glasses; barium silicates; glass properties; glass property factors; oxide glasses; silicate substructures; ternary glasses.

The glass forming regions in six ternary oxide systems containing BaO, SiO2 and a third oxide have been determined. The

properties of the resulting glasses were measured and the results are reported. The data on refractive indices, dispersions and specific volumes were evaluated by computer methods in an attempt to identify "substructures" containing the cations present in the glasses.

Monogr. 136. Graphical recoupling of angular momenta, D. R. Lehman and J. S. O'Connell, Nat. Bur. Stand. (U.S.), Monogr. 136, 18 pages (Oct. 1973) 50 cents, SD Catalog No. C13.44:136.

Key words: Angular momentum; diagrams; graphs; quantum theory; recouping; transformation theory.

A diagrammatic method for solving angular momentum recoupling problems is presented. It is shown that a few graphical elements with a set of rules for their use lead to the solution of many types of recoupling problems in an intuitive and systematic way. Several examples are given together with exercise to develop the reader's facility with the method.

Monogr. 137. Applications of waveguide and circuit theory to the development of accurate microwave measurement methods and standards, R. W. Beatty, Nat. Bur. Stand. (U.S.), Monogr. 137, 322 pages (Aug. 1973) $5.20, SD Catalog No. C13.44:137.

Key words: Attenuation definitions; attenuation measurement; barretter mount efficiency; coaxial connectors; impedance measurement; microwave network theory; mismatch errors; phase shift-measurement; power measurement; reflectometers; waveguide joints; waveguide theory. The basic theory and analytical methods used in the development of accurate microwave measurement methods and standards are presented.

Developments at the U.S. National Bureau of Standards during 1948-1968 are described in which the above theory and analytical methods were applied.

These developments were in the fields of power, impedance, attenuation and phase shift, and led to the establishment of National Standards and calibration methods at frequencies from about 300 MHz to 30 GHz.

Monogr. 138. MeV total neutron cross sections, R. B. Schwartz, R. A. Schrack, and H. T. Heaton II, Nat. Bur. Stand. (U.S.), Monogr. 138, 160 pages (Jan. 1974) SD Catalog No. C13.44:138.

Key words: MeV neutrons; neutron time-of-flight; neutron total cross sections.

This report is a compilation of the MeV neutron total cross section data measured at the National Bureau of Standards over the past several years. The measurements generally span the energy interval from 0.5 to 15 or 20 MeV; data are presented in graphical form for twelve normally occuring elements, plus the separated isotopes 235U, 238 U, and 239 Pu. An appendix is included which gives complete details of the experimental technique. Monogr. 139. Interactions of high energy particles with nuclei, W. Czyż, Nat. Bur. Stand. (U.S.), Monogr. 139, 73 pages (Sept. 1975) SD Catalog No. C13.44:139.

Key words: diffractive production; diffractive scattering; Glauber model; hadronic components of photons; high energy scattering; multiple scattering; neutrino-nucleus interactions; shadowing effects.

Elastic scattering and diffractive production processes induced in nuclear targets by high energy projectiles are discussed in this article. Special attention is paid to the interaction of high energy hadrons and photons. Interactions of high energy elec

trons and neutrinos are briefly mentioned. The common features of all these processes are emphasized throughout the article: The multiple scattering and shadowing processes inside of the target nuclei. An effort is made to develop a unified way of treating nuclear interactions of particles which are either hadrons or exhibit some hadronic components in such interactions.

This article is divided into five sections: 1) Introduction, 2) Description of multiple scattering, 3) Elastic scattering of hadrons from nuclei, 4) Diffractive dissociation and diffractive excitation, 5) Diffractive production of hadrons in hadronnucleon collisions.

Monogr. 140. Time and frequency: Theory and fundamentals, B. E. Blair, Ed., Nat. Bur. Stand. (U.S.), Monogr. 140, 470 pages (May 1974) SD Catalog No. C13.44:140.

Key words: accuracy; Allan variance; atomic frequency standards; atomic time scales; AT(NBS); BIH; buffer gases; CCIR; clock ensembles; clocks; crystal aging; Cs frequency standard; dissemination techniques; figure of merit; flicker noise; frequency stability; frequency standards; frequency/time metrology; hydrogen maser; leap seconds; Loran-C; magnetic resonance; masers; NBS-III; NBS-5; NBS/USNO time coordination; Omega; optical pumping; precision; quartz crystal oscillators; radio T/F dissemination; Rb frequency standards; satellite T/F dissemination; short-term stability; SI Units; TAI; television T/F dissemination; thallium beam standards; time; time dispersion; time domain; time/frequency statistics; time scale algorithm; time scales; "unified standard"; URSI; USA standard time zones; UTC (NBS); UTC (USNO). This is a tutorial Monograph describing various aspects of time and frequency (T/F). Included are chapters relating to elemental concepts of precise time and frequency; basic principles of quartz oscillators and atomic frequency standards; historical review, recent progress, and current status of atomic frequency standards; promising areas of developing future primary frequency standards; relevance of frequency standards to other areas of metrology including a unified standard concept; statistics of T/F data analysis coupled with the theory and construction of the NBS atomic time scale; an overview of T/F dissemination techniques; and the standards of T/F in the USA. This Monograph addresses both the specialist in the field as well as those desiring basic information about time and frequency. The authors trace the development and scope of T/F technology, its improvement over periods of decades, its status today, and its possible use, applications, and development in days to come. Monogr. 141. The measurement of lumped parameter impedance: A metrology guide, R. N. Jones, Nat. Bur. Stand. (U.S.), Monogr. 141, 211 pages (June 1974) SD Catalog No. C13.44:141.

Key words: adapters; capacitance; capacitors; detectors; generators; impedance instruments; impedance standards; inductance; inductors; measurement methods; reactance; resistance; resistor; standards.

The measurement of two-terminal impedance in the 30 kHz to 300 MHz range involves a variety of different methods including null, resonance, active and comparison. Each method is represented by a number of instruments having specific capabilities, strengths, and weaknesses. This metrology guide is intended to assist the scientist who is not intimately familiar with impedance measurement, in the selection and use of the best instrument for a particular requirement. Information is included on range and accuracy capabilities as well as availability and ease of operation. In addition to providing help in the selection of the appropriate instrument, there are operating tips which enhance accuracy, criteria for choosing standards, means for extending normal measurement range of an instrument, a discussion on generators and detectors, and a section on the evaluation and use of

adapters. Finally, an extensive bibliography is included to assist in pursuing a particular problem beyond the depth of the guide.

Monogr. 142. The measurement of noise performance factors: A metrology guide, M. G. Arthur, Nat. Bur. Stand. (U.S.), Monogr. 142, 202 pages (June 1974) SD Catalog No. C13.44:142.

Key words: effective input noise temperature; measurement errors; noise factor; noise measurements; noise performance factors; noise temperature; Y-factor measure

ments.

This metrology guide provides the basis for critical comparisons among seven measurement techniques for average noise factor and effective input noise temperature. The techniques that are described, discussed, and analyzed include the (1) Y-Factor, (2) 3-dB, (3) Automatic, (4) Gain Control, (5) CW, (6) Tangential, and (7) Comparison Techniques. The analyses yield working equations and error equations by which accuracy capabilities are compared. Each technique is also analyzed for (a) frequency range for best measurement results, (b) special instrumentation requirements, (c) speed and convenience, (d) operator skill required, and (e) special measurement problems. General instrumentation requirements and practical measurement problems are discussed for the benefit of the nonexpert metrologist. Worked examples illustrate the principles involved in applying the working and error equations. An extensive bibliography and suggested reading list aid the metrologist to locate additional material on these measurements. Taken altogether, this guide will be helpful in selecting the best measurement technique for any of a wide range of operational requirements and, once the technique is selected, it will be of further benefit in helping the metrologist identify where his efforts should be placed to derive the greatest efficiency and accuracy from his measurement system.

Monogr. 143. Analysis of optically excited mercury molecules, R. E. Drullinger, M. M. Hessel, and E. W. Smith, Nat. Bur. Stand. (U.S.), Monogr. 143, 51 pages (Jan. 1975) SD Catalog No. C13.44:143.

Key words: dissociation laser; excimers; excited state kinetics; f-values; mercury molecules; new spectroscopic techniques; optical excitation; potential curves.

The Hg molecule is representative of a class of molecules which have dissociative ground states and bound excited states. It can therefore be used as a prototype of this class of molecules which are of interest as potential new laser candidates. Because of the non-bound ground state, standard absorption spectroscopic techniques cannot be used to obtain the necessary information about the excited states. We have therefore developed new measurement techniques to obtain potential curves, f-values, and kinetic behavior for Hg. These techniques are applicable to this whole class of dissociation molecular systems.

Monogr. 144. The rotary-vane attenuator as an interlaboratory standard, W. Larson, Nat. Bur. Stand. (U.S.), Monogr. 144, 70 pages (Nov. 1975) SD Catalog No. C13.44:144.

Key words: attenuation; interlaboratory standard; measurement; rotary-vane attenuator.

This paper presents a comprehensive report on the measurement and the use of the rotary-vane attenuator as an interlaboratory standard.

Methods of attenuation measurement developed at NBS are used to supply data for the evaluation of the deviations from theoretical cos2 law due to rotor misalignment, gear eccentricity, resettability, resolution, and insufficient maximum attenuation.

A precision rotary-vane attenuator with an optical readout capable of 1 second of arc angular resolution has an effective attenuation resolution of 0.00005 dB at a 3 dB dial setting, and 0.0005 dB at a 30 dB dial setting. This type of precision attenuator is an effective standard for use in the dual detection microwave bridge measurement system.

Monogr. 145, Part I. Tables of spectral-line intensities. Part I-Arranged by elements, W. F. Meggers, C. H. Corliss, and B. F. Scribner, Nat. Bur. Stand. (U.S.), Monogr. 145, Part I, 403 pages (May 1975) SD Catalog No. C13.44:145/I.

Key words: classification of spectral lines; intensities of spectral lines; spectral-line intensities; tables of spectral-line intensities; wavelengths of spectral lines.

The relative intensities, or radiant powers, of 39 000 spectral lines with wavelengths between 2000 and 9000 Ångstroms have been determined on a uniform energy scale for seventy chemical elements. This was done by mixing 0.1 atomic percent of each element in powdered copper, pressing the powder-mixture to form solid electrodes which were burned in a 10 ampere, 220 volt direct-current arc, and photographing the spectra with a stigmatic concave grating while a step sector was rotating in front of the slit. The sectored spectrograms facilitated the estimation of intensities of all element lines relative to copper lines which were then calibrated on an energy scale provided by standardized lamps, and all estimated line intensities were finally adjusted to fit this calibration. Comparisons with other intensity measurements in individual spectra indicate that the National Bureau of Standards spectral-line intensities may have average errors of 20 percent, but first of all they provide uniform quantitative values for the seventy chemical elements commonly determined by spectrochemists. These data are presented by element in part I, and all 39 000 observed lines are given in order of wavelength in part II. Supersedes Monograph 32, Parts I and II and its supple

ment.

Monogr. 145, Part II. Tables of spectral-line intensities. Part II- Arranged by wavelengths, W. F. Meggers, C. H. Corliss, and B. F. Scribner, Nat. Bur. Stand. (U.S.), Monogr. 145, Part II, 228 pages (May 1975) SD Catalog No. C13.44:145/II.

Key words: classification of spectral lines; intensities of spectral lines; spectral-line intensities; tables of spectral-line intensities; wavelengths of spectral lines.

The relative intensities, or radiant powers, of 39 000 spectral lines with wavelengths between 2000 and 9000 Ångstroms have been determined on a uniform energy scale for seventy chemical elements. This was done by mixing 0.1 atomic percent of each element in powdered copper, pressing the powder-mixture to form solid electrodes which were burned in a 10 ampere, 220 volt direct-current arc, and photographing the spectra with a stigmatic concave grating while a step sector was rotating in front of the slit. The sectored spectrograms facilitated the estimation of intensities of all element lines relative to copper lines which were then calibrated on an energy scale provided by standardized lamps, and all estimated line intensities were finally adjusted to fit this calibration. Comparisons with other intensity measurements in individual spectra indicate that the National Bureau of Standards spectral-line intensities may have average errors of 20 percent, but first of all they provide uniform quantitative values for the seventy chemical elements commonly determined by spectrochemists. These data are presented by element in part I, and all 39 000 observed lines are given in order of wavelength in part II. Supersedes NBS Monograph 32, Parts I and II.

Monogr. 146. The theory of the optical wedge beam splitter, Y. Beers, Nat. Bur. Stand. (U.S.), Monogr. 146, 31 pages (Oct. 1974) SD Catalog No. C13.44:146.