Contains research objectives, reports on work completed and one research project.Joint Services Electronics Programs (U. S. Army, U.S. Navy, and U.S. Air Force) under Contract DA 28-043-AMC-02536(E

Espino, R. L.

Strandberg, Malcom W. P.

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IV. MICROWAVE SPECTROSCOPYAcademic and Research StaffProf. M. W. P. Strandberg J. G. IngersollDr. S. R. Reznek J. D. KiersteadGraduate StudentsJ. B. Barton L. R. Fox M. K. MaulJ. M. Ditz J. U. Free R. E. OlsenR. L. Espino R. M. Langdon, Jr. B. N. YungRESEARCH OBJECTIVESThe work of the Microwave Spectroscopy Group is of several varieties.1. Metals. We are measuring extremal sections of the Fermi surface of Ga, Cu,Sn, using dimensional resonance. With this technique one observes the variation of theelectromagnetic surface impedance of a metal single crystal at low temperatures whenthe electron orbit diameter, in a magnetic field, is equal to the crystal thickness in theplane of the orbit. Theoretical studies have been carried out to investigate the trans-port properties of these crystals under the conditions imposed by the experiment.Results on Ga indicate that APW band calculations are essentially correct.2. Electron paramagnetic resonance. This work is mainly interdisciplinary.Research in cooperation with the Department of Chemical Engineering, M. I. T., hasresulted in measurement of the reaction-rate constant for atomic hydrogen reacting withsolid propylene. The mechanics of the reaction have also been tentatively defined.A study is being made of the mechanism of electric conduction in protein molecules.3. Ultrasonics. A study of the boundary layer thermal resistance at metal-dielectric interfaces is being carried out. Also, acoustic propagation in metals atmicrowave frequencies is being studied to check out theoretical understanding of thisprocess, and, in particular, the amount of acoustic absorption, that is, the lattice-electron coupling in metals.4. Superconducting bolometers. These devices have been used as sensitive, fastdetectors of acoustic and electromagnetic energy in our laboratory. The research onthe device is directed toward work on understanding their noise properties.M. W. P. StrandbergA. WORK COMPLETED1. THE RADIO-FREQUENCY SIZE EFFECT IN ANOMALOUSSKIN DEPTH REGIONThis work has been completed by Steven R. Reznek. A thesis with this title has beensubmitted to the Department of Physics, M. I. T., in September 1967, in partial fulfill-ment of the requirements for the degree of Doctor of Philosophy. A summary of thethesis follows.This work was supported by the Joint Services Electronics Programs (U. S. Army,U. S. Navy, and U. S. Air Force) under Contract DA 28-043-AMC-02536(E).QPR No. 88(IV. MICROWAVE SPECTROSCOPY)Chapter I. The properties of the transport phenomena in a magnetic field are inves-tigated. Interest is centered upon the anomaly in the surface impedance of a metal platewhich occurs when the electron orbital diameter is commensurate with the plate thick-ness - the Radio Frequency Size Effect. The lifetimes of the electrons are consideredto be long compared with the cyclotron period, but short compared with the RF period.The orbital diameter and plate thickness are large compared with the skin depth.A method is presented for solving for the distribution function in phase space. Theimportant achievement of this method is that it correctly accounts for the collisions ofthe electrons with the surface. A line of discontinuity exists in phase space which sepa-rates trajectories that will or will not intersect the surface. This line of discontinuityis the important entity in the RF size effect.The electric and magnetic RF fields in the metal are large only near the surface.They do not decay exponentially, however. This nonexponential decay and the line ofdiscontinuity in the distribution function are responsible for the behavior of the currentdensity at distances commensurate with the orbital diameter.For distances less than one orbital diameter the current density is a constant. Fordistances greater than one orbital diameter the current density decays with a nonexpo-nential behavior. The behavior of the current density implies that the RF size-effectsignal should be smooth for DC magnetic fields smaller than H , but should wiggle forfields greater than H . H is the magnetic field at which the orbital diameter equalsthe plate thickness.Chapter II. The existing methods for studying the phenomena of the anomalous skindepth were developed to interpret cyclotron resonance. These methods begin byFourier-transforming the fundamental equations. Any Fourier-transform approach hasthe fundamental problem of convergence. The surface is a discontinuity and thesemethods are plagued by Gibb's phenomena.Chapter III. The problem of the electrons in a metal is a quantum-mechanical one.The Hamiltonian for the problem can be converted to an effective free particle Hamilto-nian by a self-consistent field approximation. The quantum-mechanical transport equa-tions are identical to the classical ones, as long as the potentials do not change rapidlyenough to "localize" a particle within its de Broglie wavelength.M. W. P. StrandbergB. REACTION OF ATOMIC HYDROGEN WITH SOLID OLEFIN FILMSAT CRYOGENIC TEMPERATURESThe reaction between hydrogen atoms and solid olefins has been studied, by usingelectron spin resonance spectroscopy, to measure the concentration of atomic hydrogenduring the course of the reaction. This experimental project was carried out during themonths of June, July, and August 1967. The use of ESR spectroscopy to monitor hydrogenQPR No. 88(IV. MICROWAVE SPECTROSCOPY)atom concentrations represents a novel and useful approach to the study of the inter-actions between an atomic species in the gas phase and a reactive solid.The experimental results have been used to determine the radical reaction mecha-nism and the reaction-rate constants. Moreover, the influence of diffusional processeson the reaction has been noticed experimentally. The experimental results have beensuccessfully used to check the validity of a reaction model based on the premise thathydrogen atoms diffuse throughout and react with the solid olefin film.R. L. EspinoQPR No. 88

Microwave Spectroscopy

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Microwave Spectroscopy

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