Rare Gas Resonance Lamps NATIONAL BUREAU of STANDARDS
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A UNITED STATES NBS TECHNICAL NOTE 496 DEPARTMENT OF COMMERCE PUBLICATION Rare Gas Resonance Lamps NATIONAL BUREAU OF STANDARDS The National Bureau of Standards ' was established by an act of Congress March 3, 1901. Today, in addition to serving as the Nation's central measurement laboratory, the Bureau is a principal focal point in the Federal Government for assuring maximum application of the physical and engineering sciences to the advancement of technology in industry and commerce. To this end the Bureau conducts research and provides central national services in four broad program areas. These are: (1) basic measurements and standards, (2) materials measurements and standards, (3) technological measurements and standards, and (4) transfer of technology. The Bureau comprises the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Center for Radiation Research, the Center for Computer Sciences and Technology, and the Office for Information Programs. THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consistent system of physical measurement; coordinates that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and com- merce. The Institute consists of an Office of Measurement Services and the following technical divisions: Applied Mathematics—Electricity—Metrology—Mechanics—Heat—Atomic and Molec- ular Physics—Radio Physics -—Radio Engineering - —Time and Frequency -—Astro- physics -—Cryogenics. 2 THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to im- proved methods of measurement standards, and data on the properties of well-characterized materials needed by industry, commerce, educational institutions, and Government; develops, produces, and distributes standard reference materials; relates the physical and chemical prop- erties of materials to their behavior and their interaction with their environments; and provides advisory and research services to other Government agencies. The Institute consists of an Office of Standard Reference Materials and the following divisions: Analytical Chemistry—Polymers—Metallurgy—Inorganic Materials—Physical Chemistry. THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services to promote the use of available technology and to facilitate technological innovation in industry and Gov- ernment; cooperates with public and private organizations in the development of technological standards, and test methodologies; and provides advisory and research services for Federal, state, and local government agencies. The Institute consists of the following technical divisions and offices: Engineering Standards—Weights and Measures — Invention and Innovation — Vehicle Systems Research—Product Evaluation—Building Research—Instrument Shops—Meas- urement Engineering—Electronic Technology—Technical Analysis. THE CENTER FOR RADIATION RESEARCH engages in research, measurement, and ap- plication of radiation to the solution of Bureau mission problems and the problems of other agen- cies and institutions. The Center consists of the following divisions: Reactor Radiation—Linac Radiation—Nuclear Radiation—Applied Radiation. THE CENTER FOR COMPUTER SCIENCES AND TECHNOLOGY conducts research and provides technical services designed to aid Government agencies in the selection, acquisition, and effective use of automatic data processing equipment; and serves as the principal focus for the development of Federal standards for automatic data processing equipment, techniques, and computer languages. The Center consists of the following offices and divisions: Information Processing Standards—Computer Information — Computer Services — Sys- tems Development—Information Processing Technology. THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and accessibility of scientific information generated within NBS and other agencies of the Federal government; promotes the development of the National Standard Reference Data System and a system of information analysis centers dealing with the broader aspects of the National Measure- ment System, and provides appropriate services to ensure that the NBS staff has optimum ac- cessibility to the scientific information of the world. The Office consists of the following organizational units: Office of Standard Reference Data—Clearinghouse for Federal Scientific and Technical Information ' —Office of Technical Information and Publications—Library—Office of Public Information—Office of International Relations. : Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington. D.C. 20234. '-' Located at Boulder. Colorado 80302. :1 Located at 5285 Port Royal Road. Springfield. Virginia 22151. UNITED STATES DEPARTMENT OF COMMERCE Maurice H. Stans, Secretary NATIONAL BUREAU OF STANDARDS • Lewis M. Branscomb, Director NBS TECHNICAL NOTE 496 ISSUED OCTOBER 1969 Nat. Bur. Stand. (U.S.), Tech. Note 496, 55 pages (Oct. 1969} CODEN: NBTNA Rare Gas Resonance Lamps R. Gorden, Jr., R. E. Rebbert, and P. Ausloos Physical Chemistry Division Institute for Materials Research National Bureau of Standards Washington, D.C. 20234 NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be listed or referred to in the open literature. For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C, 20402 - Price 60 cents Contents Page I. Introduction 1 II. General Design Characteristics 4 III. Procedure for Filling Rare Gas Resonance Lamps 7 IV. Actinometry 10 A. Apparatus and Procedure for the Measurement of Saturation Ion Currents 10 B. Extinction Coefficients and Ionization Quantum Yields for Various Substances 12 V. Xenon, Krypton and Argon Resonance Lamps 16 A. Transmission of Windows 16 B. Operational Characteristics 18 VI. Helium and Neon Resonance Lamps 20 A. Aluminum Windows 20 B. Operational Characteristics 25 1. Spectral Purity of Helium and Neon Lamps 2 5 2. Intensity of Neon and Helium Lamps 27 a) Effect of Helium and Neon Pressure ... 27 b) Effect of Power ana Distance of Discharge from Window 28 VII. References 30 li Rare Gas Resonance Lamps R. Gorden, Jr., R. E. Rebbert and P. Ausloos Rare gas resonance lamps having high spectral purity, high intensity, and long lifetimes have successfully been manufactured. The design and filling procedure for these lamps is described in detail. Particular operational characteristics of the xenon, krypton, argon, neon, and helium resonance lamps are also given. Windows suitable for use with each of these lamps are described, with particular emphasis given to the procedure for fabricating thin aluminum windows for use with neon and helium lamps. In addition, a method for determining extinction coefficients and ionization quantum yields based on the mea- surement of saturation ion currents is described. Key words: Resonance lamps; rare gases; photo- chemistry; photoionization; extinction coefficients; ionization quantum yield; aluminum window; saturation ion current. I. Introduction Light sources for use in vacuum ultraviolet photochemistry, photo- electron spectroscopy, as well as other applications, which utilize the emission of the characteristic resonance lines from excited rare gas atoms Til* (see Table I) have now been in use for a number of years. L J The rare gas resonance lamps fall into two categories according to their design; namely, those which have windows and those which are windowless. Enclosed lamps, utilizing windows which are transparent in the appropriate wavelength region, are generally fairly simple to make and to use, but until now have been restricted to the energy region including xenon, krypton, and argon resonance radiation because there was no readily available window material Figures in brackets indicate the literature references on page 30 TABLE I Lowest Resonance Emissions and Ionization Energies of the Rare Gases Resonance Emission Ionization Energy Gas (eV) (A) (eV) (A) He 21.22 584.3 24. 59 504.3 Ne 16. 85 73 5.8 21. 56 574.9 16. 67 743.7 Ar 11. 83 1048.2 15.76 786.7 11. 62 1066.7 Kr 10 64 1164.9 14.00 885.6 10 03 1235.8 Xe 9 57 1295.6 12.13 1022.1 8 44 1469.6 . 1 which would transmit photons of energy higher than 11.8 eV. Windowless lamps, on the other hand,, can utilize the rare gases which emit higher energy radiation, but are much more complicated in design since they require differential pumping and impose severe limitations on the pressure of the gas to be irradiated. It has long been known that certain metals, such as tin or aluminum, [21 or oxides such as SiO, will transmit high energy photons. J The require- ments of nuclear physics and electron microscopy have spurred the develop- ment of techniques for forming thin aluminum films supported on very fine mesh screens. If these films are sufficiently thin, yet sufficiently strong, they can be used as windows for rare gas resonance lamps. Recently, 3 1 the use of such a window on a "continuous plasma" helium lamp was reported; Lf J the lamp design described in that publication is, however, fairly complicated and difficult to fabricate and use. In this laboratory, enclosed microwave-operated xenon, krypton, and r 4 argon lamps have been in routine use for