2900- 175 - R Memorandum of Project MICHIGAN C N-NUCLEAR INTERACTION ITS EFFECT ON THE RUBY M George Makhov Robert Terhune John Lambe Lloyd Cross July 1960 SOLID - STATE PHYSICS LABORATORY T HE U NI VE R SI TY O F MI C HI GA N Ann Arbor, Michigan

DISTRIBUTION OF REPORTS Distribution control of Project MICHIGAN Reports has been delegated by the U. S. Army Signal Corps to: Commanding Officer U. S. Army Liaison Group Project MICHIGAN Willow Run Laboratories Ypsilanti, Michigan it is requested that information or inquiry con cerning distribution of reports be addressed accordingly. Project MICHIGAN is carried on for the U. S. Army Signal Corps under Department of the Army Prime Contract Number DA-36-039 SC-78801. University contract administration is provided to Willow Run Laboratories through The University of Michigan Research Institute.

ILLW RUN LABRATORIES TECHNICAL MEMORANDUM PREFACE Documents issued in this series of Technical Memorandums are published by Willow Run Laboratories in order to disseminate scientific and engineering information as speedily and as widely as possible. The work reported may be incomplete, but it is considered to be useful, interesting, or suggestive enough to warrant this early publication. Any conclusions are tentative, of course. Also included in this series will be reports of work in progress which will later be combined with other materials to form a more comprehensive contribution in the field. A primary reason for publishing any paper in this series is to invite technical and professional comments and suggestions. All correspondence should be addressed to the Technical Director of Project MICHIGAN. Project MICHIGAN, which engages in research and development for the U. S. Army Combat Surveillance Agency of the U. S. Army Signal Corps, is carried on by Willow Run Laboratories as part of The University of Michigan's service to various government agencies and to industrial organizations. Robert L. Hess Technical Director Project MICHIGAN

WI LLOW RUN LABORATORIES TECHNICAL MEMORANDUM ELECTRON-NUCLEAR INTERACTION IN RUBY AND ITS EFFECT ON THE RUBY MASER ABSTRACT It has been found that changes in the polarization of the Al27 and Cr 53nuclei in ruby affect markedly the absorption or emission of microwave power associated with the electron-spin resonance of the Cr+++ ion. This effect has been used to observe weak nuclear resonances and to change markedly the operating characteristics of the maser. INTRODUCTION One need hardly emphasize the advantages of a maser device which is capable of amplifying microwave energy and which, simultaneously, possesses low-frequency output. Such a device combines the practically noise-free amplification characteristics of the maser with the convenience of a radio-frequency output stage. In the case of solid-state masers, this device can be conceivably realized by making use of electron-nuclear interactions. These interactions couple the paramagnetic resonance, which occurs at microwave frequencies, with the nuclear resonance which occurs at frequencies of the order of megacycles or of tens of megacycles. While electron-nuclear interactions have been observed in a number of paramagnetic materials, little is yet known of their exact nature. This is partly because of the complexity of the processes involved, but also partly because of the scarcity of pertinent experimental data. Accordingly, an experimental study is being conducted at Willow Run Laboratories which is directed at gathering data which may provide insight into the mechanism of electronnuclear interaction. The initial results of this study are reported here. 1

WILLOW RUN LABORATORIES TECHNICAL MEMORAN DUM 2 ELECTRON-NUCLEAR INTERACTION WITH ELECTRON-SPIN SYSTEM AT POSITIVE TEMPERATURE The polarization of nuclear spins throughout a crystal by saturation of an electron-spin resonance of paramagnetic ions present as impurities has recently been reported (References 1 and 2). An apparent inverse of this effect in ruby (Al203:0.05% Cr ) has been observed at Willow Run Laboratories; i. e., when the induced nuclear polarization is partially removed by saturating an aluminum nuclear spin-resonance transition, a large decrease in the power absorbed by the electron-spin resonance of the Cr ions is observed. Effects associated with induced transitions between the hyperfine levels of the Cr ions have also been observed. Magnetic-field modulation at 5 kc was used to observe the edge of the (+1/2 = -1 /2) electron-spin-resonance absorption line of ruby with a microwave power level about 20 db above saturation. The spectrum shown in Figure 1 was then obtained by scanning the frequency of a low-power r-f oscillator connected to a single turn of wire around the ruby sample. The five lines in the 3-mc region correspond very well to the nuclear-magnetic-resonance spectrum of the host aluminum nuclei in the crystal. The same dependence of the splitting between lines upon the angle of d-c magnetic field and line width were observed both here and in the nuclear-magnetic-resonance spectrums. ~co,,~~~ ~S =-1/2 0 S =+1/2 S =+3/2 cz 2.6 3.0 3.4 3.8 23 25 27 29 73 74 75 76 FREQUENCY IN MEGACYCLES 27 53 FIGURE 1. Al AND Cr NUCLEAR RESONANCES IN RUBY. 0 = 0. 53 The lines near 25 and 75 mc are associated with the I- S splitting of the Cr ions (Reference 3) which have a nuclear spin of 3/2 and a natural abundance of 9. 5%. The other isotopes of chromium all have zero nuclear spin. The +1/2 and +3/2 electron-spin states

WI LLOW RUN LABORATORIES TECH NICAL MEMORANDUM are very close together at our operating point. As a result they interact strongly as the angle of the d-c magnetic field is varied, causing large changes in the hyperfine splitting (Figure 2). Also, the second-order correction to their hyperfine splitting is appreciable and leads to the observed triplets. The strength of the lines reduced very rapidly with departure from zero degrees. A weak triplet associated with S = -3/2 was also observed with the lines falling at 71. 93, 72. 15, and 72. 37 mc at zero degrees. It is interesting to note that though all the Cr53 data were taken by observing the S = -1/2 to +1/2 transition, saturation of the hyperfine levels in the S = +3/2 state caused the largest changes in the electron-spin-resonance signal. 75 S =+3/2: 65 55'~ I i I S =+1/2 h; 45 O 35 S =-1/2 25 __0 2 4 6 8 10 ANGLE IN DEGREES BETWEEN C AXIS AND MAGNETIC FIELD 53 FIGURE 2. ANGULAR DEPENDENCE OF THE Cr SPECTRUM The strong effect of nuclear polarization on the electron-spin resonance can easily be observed in ruby without applying r-f power. At microwave power level well above saturation, if one rapidly moves from one part of the resonance line to another a large transient with a decay time of about 5 seconds is observed. The same decay time is observed for the transient following removal of r-f power sufficient to saturate one of the aluminum nuclear transitions. Further, the observed decay time of the aluminum nuclear polarization is also 5 seconds and T1 (spin-lattice relaxation time) for the electron-spin-resonance transition is approximately 3

WI LLOW RUN LABORATORIES TECHNICAL MEMORANDUM 0. 2 second. The decay time of the effects associated with the Cr nuclei was also near 5 seconds. The effects of nuclear polarization upon the electron-spin-resonance signal were only observable when microwave power levels of the order of or greater than that needed to saturate the electron-spin transition was used. When the electron-spin-resonance signal was observed at low microwave powers, the application of r-f power had no effect upon the signal. Further, when the signal was observed during the nuclear-polarization relaxation time following a quick reduction in the microwave power level from above to well below saturation, only a 0. 2-second time-constant transient was observed. The application of r-f power had no effect upon the transient, thereby indicating that T1 is independent of the nuclear polarization. A decrease in microwave power absorption with the application of r-f power was always observed. As a check, some observations were made using amplitude modulation of the microwaves rather than magnetic-field modulation. Also, the amplitude of the magnetic-field modulation was varied over a wide range with no significant effects being observed. It does not seem that the effects reported here can be explained by any of the mechanisms proposed by Feher (References 4 and 5) to explain his observations in doped silicon. The slow relaxation after the removal of r-f power would seem to indicate that the host nuclei play an important role in either the induced transition probabilities or the relaxation mechanism between electron-spin states. If so, in order to get an appreciable percentage effect in the electron system by saturating the nuclei one would have to reduce the relative electronic polarization ) to the same order as the nuclear polarization (); i.e. =. This idea is consistent with our experimental results because the nuclear polarizations are increased by a factor of about 40 (Reference 1) and the electronic polarizations are decreased by a factor of about 100 under our experimental conditions; thus the two are made comparable. 3 ELECTRON-NUCLEAR INTERACTION WITH ELECTRON-SPIN SYSTEM AT NEGATIVE TEMPERATURE The effect of electron-nuclear interaction on the behavior of the ruby maser is of considerable interest. In the basic experiment, a two-turn coil was wound about a ruby sample containing, nominally, 0.1% chromium. This assembly was placed in a doubly resonant microwave cavity and located in the d-c magnetic field in such a manner that the axis of the coil was perpendicular to the direction of the field, and the polar angle was approximately 600. With

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM the system cooled to 4. 20K, a K-band microwave pump was used to saturate the 1-3 transition, and stimulated emission at X-band frequency was obtained in the 3-2 transition. Subsequent application of r-f power at 4. 2 mc produced an increase in the gain of the maser amplifier, and resulted in a change in the mode of operation of the maser oscillator. The effect was most pronounced at the resonant frequency of the free-aluminum nuclei; however, at higher levels of r-f power substantial interaction was obtained over a band extending from 500 kc to 20 mc. Typically, power levels required to produce a detectable effect were of the order of 10 mw on resonance, and about an order of magnitude higher off resonance. When the performance of the maser amplifier with r-f power on and off is compared, as shown in Figures 3(a) and 3(b), respectively, the change in the magnetic Q due to the change in polarization of the aluminum nuclei may be calculated. The change in gain amounted to 20 db. The dependence of the maser amplifier's gain on the magnetic Q is given by I 1 1 2 G = IQ 1 1 1 2 where Qc is the coupling Q, QL is the loss Q, and Qm is the negative magnetic Q. In our arrangement, Qc and QL are typically 103. With this value, the decrease in Qm due to the application of r-f power was computed to be approximately 20%. This change in magnetic Q was observed under conditions of partial saturation of the pumping transition, and on the lowfield side of the EPR (electron paramagnetic resonance) line. FIGURE 3. EFFECT OF CHANGE OF NUCLEAR POLARIZATION ON BEHAVIOR OF MASER AMPLIFIER. (a) r-f off; power gain = 15 db. (b) r-f on; power gain = 35 db.

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM The effect of decreased nuclear polarization on the behavior of the maser oscillator is shown in Figure 4. The application of r-f power tended to make the transient of the c-w mode of the oscillator (Figure 4a) less damped, and led eventually to the relaxation mode of operation (Figure 4b). The use of high r-f power levels tended to diminish or even reverse the effect. FIGURE 4. EFFECT OF CHANGE OF NUCLEAR POLARIZATION ON BEHAVIOR OF MASER OSCILLATOR. (a) r-f off; c-w mode of operation. (b) r-f on; relaxation mode of operation. It should be noted that the transient form of the interaction, as in the case of resonant absorption, can be observed without the use of r-f power. When maser action is initiated by bringing the d-c magnetic field rapidly to the appropriate value, a transient results during which the amplifier gain rises quickly to a high value, then decays slowly to a lower steadystate value. The time constant of the transient is seconds in duration. The existence of the transient cannot be ascribed to spin-lattice relaxation since T1 for cooled ruby is of the order of 0. 1 second. Rather, it appears to be due to the relaxation of the polarization of aluminum nuclei. Subsequent experiments have indicated that the application of r-f power does not affect thermal-relaxation processes to any perceptible degree. Rather, the application of r-f power can be thought of as added pumping, resulting in an increase in the magnetic Q. The degree of enhancement of the pumping process is of the order of the change in the degree of nuclear polarization, extimated to be about 1% under our experimental conditions. Under conditions of 6i

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM marginal saturation of the pumping transition, this may lead to a substantial decrease in the magnetic Q, as noted above. These considerations suggest that the recovery of a solid-state maser device from saturation, or from fluctuations in pumping power, is characterized in general by two time constants. There is rapid recovery, of the order of 0. 1 second, determined by spin-lattice relaxation; and slow recovery, seconds in duration, determined by nuclear-electronic relaxation. These effects have been observed experimentally. The latter effect, of course, becomes significant only when the on-period of the saturating signal, or variations in the degree of saturation of the pumping transition, are on a time scale comparable to that of nuclear relaxation. In conclusion we would like to conjecture that the observed increase in gain of the maser amplifier due to application of r-f power may be used to advantage in detecting weak nuclear resonances as well as in studies of ENDOR-type (electron-nuclear double resonance) effects. In essence, the effect on the electron system produced by the resonant pumping of the nuclear system is amplified by the practically noiseless maser amplifier. When a high degree of regeneration is used, a small change in the magnetic Q results in a very considerable change in gain, or output (as attested by Figures 3a and 3b, and the corresponding calculation). A disadvantage of this method is that maser action cannot be obtained in ruby in the vicinity of 0 = 0~, whereas nuclear resonance effects are conveniently observed at that orientation. Presumably, this can be remedied by using a paramagnetic material, such as iron-doped sapphire, which permits maser action at the above orientation. RE FERENCES 1. J. A. Cowen, R. W. Schafer, and R. D. Spence, Phys. Rev. Letters, 1959, Vol. 3, p. 13. 2. M. Abraham, M. A. H. McCausland, and F. N. H. Robinson, Phys. Rev. Letters, 1959, Vol. 2, p. 449. 3. A. A. Manenkov, and A. M. Prokhorov, Zhur. Eksperi, Theoret. Fiz., 1956, Vol. 31, No. 2(8), pp. 346-347. 4. G. Feher, Phys. Rev., 1959, Vol. 114, p. 1219. 5. G. Feher, and E. A. Gere, Phys. Rev., 1959, Vol. 114, p. 1245.

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM DISTRIBUTION LIST 6, PROJECT MICHIGAN REPORTS 1 July 1960-Effective Date Copy No. Addressee Copy No. Addressee 1 Office, Chief of Research& Development 44 Director, U. S. Army Engineering Research Department of the Army, Washington 25, D. C. & Development Laboratories ATTN: Army Research Office Fort Belvoir, Virginia ATTN: Army Research Office ATTN: Technical Document Center 2 Office, Assistant Chief of Staff for Intelligence Department of the Army, Washington 25, D. C. 45 Commandant, U. S. Army Command & General Staff ATTN: Chief, Combat Development/G-2Air Branch College Fort Leavenworth, Kansas 3 Commanding General, U. S. Continental Army Command ATTN: Archives Fort Monroe, Virginia 46 Commanding General, U. S. Army Combat Development Experimentation Center 4-5 Fort Ord, California 4-5 Commanding General, U. S. Army Combat Surveillance Fort Ord, California Agency 47-48 Assistant Command, U. S. Army Artillery & 1124 N. Highland Street, Arlington 1, Virginia Missile School Fort Sill, Oklahoma 6 Chief, Research & Development Division Fort Sill, Oklahoma Office of the Chief Signal Officer 49-51 Assistant Commandant, U. S. Army Air Defense School Department of the Army, Washington 25, D. C. Fort Bliss, Texas 7-31 Commanding Officer, U. S. Army Signal Research & 52 Commandant, U. S. Army Engineer School Development Laboratory Fort Belvoir, Virginia Fort Monmouth, New Jersey ATTN: Combat Development Group ATTN: SIGFM/EL-DR 53 Commandant, U. S. Army Signal School 32-33 Commander, ArmyRocket & Guided Missile Agency Fort Monmouth, New Jersey Redstone Arsenal, Alabama ATTN: SIGFM/SC-DO ATTN: Technical Library, ORDXR-OTL 54 Commandant, U. S. Army Aviation School 34-35 Chief, U. S. Army Security Agency Fort Rucker, Alabama Arlington Hall Station, Arlington 12, Virginia 55-57 President, U. S. Army Artillery Board 36 Office of the Director, Defense Research & Engineering Fort Sill, Oklahoma Technical Library Department of Defense, Washington 25, D. C. 58 President, U. S. Army Air Defense Board Fort Bliss, Texas 37 Commanding General, Quartermaster Research& Engineering Command 59 President, U. S. Army Airborne& Electronics Board U. S. Army, Natick, Massachusetts Fort Bragg, North Carolina 38 Office, Chief of Ordnance, 60 Commanding Officer, U. S. Army Signal Electronic Research & Development Division Research Unit Department of the Army, Washington 25, D. C. Post Office Box 205, Mountain View, California ATTN: ORDTB, Research & Special Projects 61 Office of Naval Operations Department of the Navy, Washington 25, D. C. 39 Commanding General, U. S. Army Electronic Proving Ground ATTN: OP-37 Fort Huachuca, Arizona ATTN: Technical Lirary 62 Office of Naval Operations Department of the Navy, Washington 25, D. C. 40 Chief of Engineers ATTN: OP-07T Department of the Army, Washington 25, D. C. ATTN:Reseach.tDivision.63-65 Office of Naval Research, Department of the Navy 17th & Constitution Ave., N. W., Washington 25, D. C. 41 Director, U. S. Army Engineer Research ATTN: Code 463 & Development Laboratories Fort Belvoir Virginia 66 Chief, Bureau of Ships Department of the Navy, Washington 25, D. C. ATTN: Chief, Topographic Engineering Department Department of the Navy, Washington 25, D. C. ATTN: Code 690 42-43 Director, U. S. Army Engineering Research & Development Laboratories 67-68 Director, U. S. Naval Research Laboratory Fort Belvoir, Virginia Washington 25, D. C. ATTN: Chief, Electrical Engineering Department ATTN: Code 2027

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM DISTRIBUTION LIST 6 1 July 1960- Effective Date Copy No. Addressee Copy No. Addressee 69 Commanding Officer, U. S. Navy Ordnance Laboratory 103 Commander, Rome Air Development Center Corona, California Griffiss Air Force Base, New York ATTN: Library ATTN: RCWIR 70 Commanding Officer & Director 104 Director, Air University Library U. S. Navy Electronics Laboratory Maxwell Air Force Base, Alabama San Diego 52, California ATTN: AUL-7971 ATTN: Library 105 Commandant of the Marine Corps, Headquarters 71 Department of the Air Force U. S. Marine Corps, Washington 25, D. C. Headquarters, USAF, Washington 25, D. C. ATTN: CodeA04E ATTN: AFOIN-1B1 106-109 Central Intelligence Agency 72 Department of the Air Force 2430 E. Street, N. W., Washington 25, D. C. Headquarters, USAF, Washington 25, D. C. ATTN: OCR Mail Room ATTN: AFOAC-E/A 110-114 National Aeornautics & Space Administration 73 Department of the Air Force 1520 H. Street, Northwest, Washington 25, D. C. Headquarters, USAF, Washington 25, D. C. ATTN: AFDRD 115-116 Combat Surveillance Project Cornell Aeronautical Laboratory, Incorporated 74 Department of the Air Force Box 168, Arlington 10, Virginia Headquarters, USAF, Washington 25, D. C. ATTN: Technical Library ATTN: Directorate of Requirements 117 The RAND Corporation 75 Commander in Chief, Headquarters, Strategic 1700 Main Street, Santa Monica, California Air Command ATTN: Library Offutt Fir Force Base, Nebraska ATTN: DINC 118 Chief Scientist, Research & Development Division Office of the Chief Signal Officer 76 Headquarters, Tactical Air Command Department of the Army, Washington 25, D. C. Langley Air Force Base, Virginia 119 Stanford Research Institute, Document Center Menlo Park, California 77-78 Commander in Chief, Headquarters, Strategic Air ATTN: Acquisitions Command Offutt Air Force Base, Nebraska 120 Operations Research Office The Johns Hopkins University 6935 Arlington Road, 79-80 Headquarters, Tactical Air Command Bethesda, Maryland, Washington 14, D. C. 79-80 Headquarters, Tactical Air Command Langley Air Force Base, Virginia ATTN: Chief Intelligence Division ATTN: TORQ 121 Columbia University, Electronics Research Laboratories 632 W. 125th Street, New York 27, New York 81 Commander, Air Technical Intelligence Center 632 W. 125th Street, New York 27, New York Wright-Patterson Air Force Base, Ohio ATTN: Technical Library ATTN: AFCIN-4B/a VIA: Commander, Rome Air Development Center Griffiss Air Force Base, New York 82-91 ASTIA (TIPCR) Arlington Hall Station, Arlington 12, Virginia 122-123 Cornell Aeronautical Laboratory, Incorporated 92-100 Commander, Wright Air Development Division4455 Genesee Street, Buffalo 21, New York Wright-Patterson Air Force Base, Ohio ATTN: Librarian ATTN: WCLROR VIA: Bureau of Aeronautics Representative 101 Commander, Wright Air Development Division 4455 Genesee Street, Buffalo 21, New York Wright-Patterson Air Force Base, Ohio 124 Control Systems Laboratory University of Illinois, Urbana, Illinois 102 Commander, Rome Air Development Center ATTN: Librarian Griffiss Air Force Base, New York VIA: ONR Resident Representative ATTN: RCVSL-1 1209 W. Illinois Street, Urbana, Illinois

WILLOW RUN LABORATORIES TECHNICAL MEMORANDUM DISTRIBUTION LIST 6 1 July 1960- Effective Date Copy No. Addressee Copy No. Addressee 125 Polytechnic Institute of Brooklyn 128 U. S. Continental Army Command, Liaison Officer 55 Johnson Street, Brooklyn 1, New York Project MICHIGAN, Willow Run Laboratories Ypsilanti, Michigan ATTN: Microwave Research Institute Library 126 The U. S. Army Aviation HRU P. O. Box 428, Fort Rucker, Alabama 127 Director, Electronic Defense Group 129 Commanding Officer, U. S. Army Liaison Group University of Michigan Research Institute Project MICHIGAN University of Michigan, Ann Arbor, Michigan Willow Run Laboratories, Ypsilanti, Michigan

AD Div. 25/8 UNCLASSIFIED AD Div. 25/8 UNCLASSIFIED Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Maser-Operation Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Maser-Operation ELECTRON-NUCLEAR INTERACTION IN RUBY AND ITS EFFECT 2. Synthetic ruby ELECTRON-NUCLEAR INTERACTION IN RUBY AND ITS EFFECT 2. Synthetic ruby ON THE RUBY MASER by George Makhov, Robert Terhune, John I. Project MICHIGAN ON THE RUBY MASER by George Makhov, Robert Terhune, John I. Project MICHIGAN Lambe, Lloyd Cross. Memorandum of Project MICHIGAN. July 60, II. Makhov, George, Terhune, Lambe, Lloyd Cross. Memorandum of Project MICHIGAN. July 60, II. Makhov, George, Terhune, 7 p. incl. illus., 5 refs. Robert, Lambe, John, 7 p. incl. illus., 5 refs. Robert, Lambe, John, (Memo no. 2900-175-R) Cross, Lloyd (Memo no. 2900-175-R) Cross, Lloyd (Contract DA-36-039 SC-78801) Unclassified memorandum III. U. S. Army Signal Corps (Contract DA-36-039 SC-78801) Unclassified memorandum III. U. S. Army Signal Corps It has been found that changes in the polarization of the Al27 and Cr53 IV. Contract DA-36-039 It has been found that changes in the polarization of the Al27 and Cr53 IV. Contract DA-36-039 SC-78801 ~~~~~~~~~~~~~~~~~~~~~~~~~SC-78801 nuclei in ruby affect markedly the absorption or emission of micro- SC-78801 nuclei in ruby affect markedly the absorption or emission of micro- SC wave power associated with the electron-spin resonance of the Cr+++ wave power associated with the electron-spin resonance of the Cr+++ ion. This effect has been used to observe weak nuclear resonances and ion. This effect has been used to observe weak nuclear resonances and to change markedly the operating characteristics of the maser. Armed Services to change markedly the operating characteristics of the maser. Armed Services (over) Technical Information Agency (over) Technical Information Agency UNCLASSIFIED UNCLASSIFIED + AD Div. 25/8 UNCLASSIFIED AD Div. 25/8 UNCLASSIFIED Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Maser-Operation Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Maser-Operation ELECTRON-NUCLEAR INTERACTION IN RUBY AND ITS EFFECT 2. Synthetic ruby ELECTRON-NUCLEAR INTERACTION IN RUBY AND ITS EFFECT 2. Synthetic ruby ON THE RUBY MASER by George Makhov, Robert Terhune, John I. Project MICHIGAN ON THE RUBY MASER by George Makhov, Robert Terhune, John I. Project MICHIGAN Lambe, Lloyd Cross. Memorandum of Project MICHIGAN. July 60, II. Makhov, George, Terhune, Lambe, Lloyd Cross. Memorandum of Project MICHIGAN. July 60, II. Makhov, George, Terhune, 7 p. incl. illus., 5 refs. Robert, Lambe, John 7 p. incl. illus., 5 refs. Robert, Lambe, John, (Memo no. 2900-175-R) Cross, Lloyd (Memo no. 2900-175-R) Cross, Lloyd (Contract DA-36-039 SC-78801) Unclassified memorandum HI. U. S. Army Signal Corps (Contract DA-36-039 SC-78801) Unclassified memorandum III. U.S. Army Signal Corps It has been found that changes in the polarization of the Al27 and Cr53 IV. Contract DA36039 It has been found that changes in the polarization of the Al27 and Cr53 IV. Contract DA-36-039 nuclei in ruby affect markedly the absorption or emission of micro- SC-78801 nuclei in ruby affect markedly the absorption or emission of micro- SC-78801 wave power associated with the electron-spin resonance of the Cr+++ wave power associated with the electron-spin resonance of the Cr+++ ion. This effect has been used to observe weak nuclear resonances and ion. This effect has been used to observe weak nuclear resonances and to change markedly the operating characteristics of the maser. Armed Services to change markedly the operating characteristics of the maser. Armed Services (over) Technical Information Agency (over) Technical Information Agency UNCLASSIFIED UNCLASSIFIED t1- +

AD UNCLASSIFIED AD UNCLASSIFIED UNITERMS Polarization Polarization A127 A127 Cr53 Cr53 Ruby Ruby Electron-spin Electron-spin Resonance Resonance Maser Maser UNCLASSIFIED UNCLASSIFIED AD UNCLASSIFIED AD UNCLASSIFIED UNITERMS UNITERMS Polarization Polarization A127 A127 Cr53 Cr53 Ruby Ruby Electron-spin Electron-spin Resonance Resonance Maser Maser UNCLASSIFIED UNCLASSIFIED

+ + AD Div. 25/8 UNCLASSIFIED AD Div. 25/8 UNCLASSIFIED Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Maser-Operation Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Maser-Operation ELECTRON-NUCLEAR INTERACTION IN RUBY AND ITS EFFECT 2. Synthetic ruby ELECTRON-NUCLEAR INTERACTION IN RUBY AND ITS EFFECT 2. Sythetic rby ON THE RUBY MASER by George Makhov, Robert Terhune, John I. Project MICHIGAN ON THE RUBY MASER by George Makhov, Robert Terhune, John I. Project MICHIGAN Lambe, Lloyd Cross. Memorandum of Project MICHIGAN. July 60, II. Makhov, George, Terhune Lambe, Lloyd Cross. Memorandum of Project MICHIGAN. July 60, II. Makhov, George, Terhune, 7 p. incl. illus., 5 refs. Robert, Lambe, John, 7p. incl. illus, 5refs Robert, Lambe, John, (Memo no. 2900-175-R) Cross, Lloyd (Memo no. 2900-175-R) Cross, Lloyd (Contract DA-36-039 SC-78801) Unclassified memorandum III. U. S. Army Signal Corps (Contract DA-36-039 SC-78801) Unclassified memorandum III. U. S. Army Signal Corps It has been found that changes in the polarization of the Al27 and Cr53 IV. Contract DA-36-039 It has been found that changes in the polarization of the Al27 and Cr53 IV. Contract DA-36-09 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~SC-78801 nuclei in ruby affect markedly the absorption or emission of micro- SC-78801 nuclei in ruby affect markedly the absorption or emission of micro- C wave power associated with the electron-spin resonance of the Cr+++ wave power associated with the electron-spin resonance of the Cr+++ ion. This effect has been used to observe weak nuclear resonances and ion. This effect has been used to observe weak nuclear resonances and to change markedly the operating characteristics of the maser. Armed Services to change markedly the operating characteristics of the maser. Armed Services (over) Technical Information Agency (over) Technical Information Agency UNCLASSIFIED UNCLASSIFIED + AD Div. 25/8 UNCLASSIFIED AD Div. 25/8 UNCLASSIFIED Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Maser- Operation Willow Run Laboratories, U. of Michigan, Ann Arbor 1. Maser-Operation ELECTRON-NUCLEAR INTERACTION IN RUBY AND ITS EFFECT 2. Synthetic ruby ELECTRON-NUCLEAR INTERACTION IN RUBY AND ITS EFFECT 2. Synthetic ruby ON THE RUBY MASER by George Makhov, Robert Terhune, John I. Project MICHIGAN ON THE RUBY MASER by George Makhov, Robert Terhune, John I. Project MICHIGAN Lambe, Lloyd Cross. Memorandum of Project MICHIGAN. July 60, II. Makhov, George, Terhune Lambe, Lloyd Cross. Memorandum of Project MICHIGAN. July 60, II. Makhov, George, Terhune, 7p. incl. illus., 5 refs. Robert, Lambe, John 7p. incl. illus., 5 refs. Robert, Lambe, John, (Memo no. 2900-175-R) Cross, Lloyd (Memo no. 2900-175-R) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~(Memo no. 2900-175-H) Cross, Lloyd (Contract DA-36-039 SC-78801) Unclassified memorandum mH. U. S. Army Signal Corps (Contract DA-36-039 SC-78801) Unclassified memorandum III. U.S. Army Signal Corps It has been found that changes in the polarization of the Al27 and Cr53 IV. Contract DA-36-039 It has been found that changes in the polarization of the Al27 and Cr53 IV. Contract DA-36-039 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~SC-78801 nuclei in ruby affect markedly the absorption or emission of micro- SC-78801 nuclei in ruby affect markedly the absorption or emission of micro~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~nuclei in ruby affect markedly the absorption or emission of microwave power associated with the electron-spin resonance of the Cr wave power associated with the electron-spin resonance of the Cr+++ ion. This effect has been used to observe weak nuclear resonances and ion. This effect has been used to observe weak nuclear resonances and to change markedly the operating characteristics of the maser. Armed Services to change markedly the operating characteristics of the maser. Armed Services (over) Technical Information Agency (over) Technical Information Agency UNCLASSIFIED UNCLASSIFIED th + -1

AD ~~~|AD UNCLASSIFIED AD UNCLASSIFIED UNITERMSUNITERMS Polarization A127~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Polarization A127 Cr53 Ruby Electron-spin Ruby Resonance Electron -spin aeResonance Maser UNCLASSIFIED N ~~~~~~~~~~~~~~~~~~~~~~~~AD | UNCLASSIFIED AD | ~~~~UNCLASSIFIEDA UNITERMSUIEM Polarization A127Po =t Ruby ~~Electron~. -spin —- R o~ Resonance Eeto si MaserMae UNCLASSIFIEDUNCLA0AD UNCLASSIFIED AD UCASFE UNITERMS UIEM Polarization Plrzto Al53 Al27 Cr53 ~~~~~~~~~~~~~~~~~~~~~~~~~~Cr53 Ruby Rb Electron-spinElcrnsi ResonanceReoac MaserMae UNCLASSIFIED UCASFE