Hashi, Tsuneo

Ogawa, Toru

Okaya, Akira

Takahashi, Isao

English

Kyoto University Research Information Repository

RIGHT:URL:CITATION:AUTHOR(S):ISSUE DATE:TITLE:1.5 cm Wave-length MicrowaveSpectroscopeTakahashi, Isao; Okaya, Akira; Ogawa, Toru; Hashi,TsuneoTakahashi, Isao ...[et al]. 1.5 cm Wave-length Microwave Spectroscope. Memoirs of theCollege of Science, University of Kyoto. Series A 1950, 26(1-2): 113-1211950-10-31http://hdl.handle.net/2433/257350IsaoMemoirs of the College of gcience, University of Kyoto, Series A,          Vol, XXVI, Nos. 1 & 2, Article 12, 1950.].5 om SVave-length Mierowave Spectroseope"                        ByTakahashi, Akira Okaya, Toru Ogawa, and Tsuneo Hashi                (Received June 30, 1950)1. Introduction   In U.S.A., the field of microwave speetroscopy has grown witihtremendous rapidity in post war years, but in our coun'bry, theresearchesin this field have been scarce so far.   In compliance with the physical importanee of this field, we havedesigned and constructed the 1.5cm wave-Iength spectroseope, whosegeneral view is given in Fig. 1. 'NVith this set, we observed the ab-sorption Iine of [MIethyl Bromide (CH3Br). Our observed wave-lengbhof maximum ab,gorption eoincides with the theore'bical valrie wi'bhin the,x;X$' '"•- .- • 1ew,-   '       ''/• '•--e,tipa;. '    lii'tsa'      .,""'•    'i'         '    i'     •iitw1li[,.,,..* Bead on May 1, 1950, at the gociety of Japan.es ma,t  -g, epEWmeeting of Microwave Physics-i' ,3i\iViT ..... • "";ag;,.-1.va- /partBranch of the Physieal114 l. Tahahashi, A. Oleaya, T. Ogatua, and T. Hashi.error of our cavity wave meter and we confirmecil the hyperfine struetureof spectral line due to the presence of the quadrupole moment of Brnucleus. ,   Several accurate measurements about Methyl Bromide have alreadybeen reported by others (11, 12, 13, 14, 15). Methyl Bromide was usedm our measurement too, since it is appropriate for checking our setand in our eountry no experimenbal report about centimeter wavespectrum has hitherto been given.ce*  -:ul•i•u, l;•;it;- •mpnl.,"i'''"tw, t;.. :.li-S. h.. ','i.. ;;N.. •ctf'lh"•"sdie'teag•    .••;1i-;'    Fig. 1. General view of 1.5cm microwave spectroscope. b) The right part2. Description of the set and its cbmponents   The block diagram of our microwave spectroscope is shown in Fig. 2.A part of 3cm microwave energy from the signal osciltator, passingthrough T-junction and attenuator A, is conver"ted to 1.5cm energyby the frequeney converter. This converted energy is then led intothe absorption cell formed by a e' ircular cylinder and transparent micawindows at its both ends.   The original 3cm energy is frequency-modulated by the saw-toothgenerator and consequently the 1.5cm is so also. Thus, if the fre-quency of the converted energy is tuned to the absorption frequency of** We are aware of only Prof. Kojirna's spectroscopie researches with 12em wave-   length inicrowave which are carried on at Tokyo Edueational University. He also   has read his paper on May 1, 1950.              1.5em Mave-length ]ficro2vave Spaeetroseopat 115the sample in the cell, the emergy going out from the eell is muehdamped.   The outpnt energy amplitude-moclulatecl corresponding to the degreeoÅí absorption of the sampie in the cell is cleteetecl by the erystal deteetorand the cleteetecl power which represents tke absorption character ofthe sample is ampiifiecl and appliecl to the vertical axis of the osciilo-graph whose horizon'tal axis is swept by the vokage of the saw-toothgenerator.. [I]hws, the absorption eharaeter of the sample is v!sualizeClon the $ereen oÅí the o$eiliogr.reph.   In oiir set, the amplifieation oÅí detected power is carried otit in'bwo ways. One way is the c/lireet amplifieation by che video amplifier,ancl the other consists in rnoclifying the signal generator with 463 ke/g.ecsource modulator in addition to the saw-tooth generator and ampliÅíyingand (.leteeting by nieans of 463kc/sec narrow bantt i'eceiver.                                            '                                       3cm Wave Guide     5cm Signal Generator                                     M-                                                             o,               Ltr                 2K25    Saw-toeth                                        AttenuaÅíer   Generator E-L" esysÅírc T'crUnctiOn A  c)• il>-l}g63 y.clsS"urceModulater        Wavfl Me'Ler23 CavitytrEen)Slitrsrystal.Å~-    anI 'Å~.' Taperea W&ve Guiae frgm l'5cm (TEoi) =Lo 3emCTE2i)A-.b-lo-rtethion CellXt:.g'2-9m lens`th([[I!Iil)Osciliograph ST'sOOIA.*.ieÅë•g               ut .il'Ls   as3Ke,/st{arrew Bana  ReÅëe'v VickeoAR, iplifie?l {ve!'t. SIQri11'5cmWaveGuiae           IFig. 2. Bloclc diagram of 1.5cm micro"'ave spectroscope.   Xn Che folloxving, the main eomlponents of tl]e set are describecl.(1) Signal Geneo'ato?': [I]he well-knoxvn I{lystron tube 2I<125 is iiseclai}d its 'freqllency i'ange is from 8.5 to 9..8kMclsec.(2) Fregzoen,ey aonverter : As shown in Fi.cr. 3, it is composecl of riclgetype wave gnicle, coaxial line a,n(rl silicon crystai IN23. [[ro designthe riclge type wave guicle, some pa, pers (2, 3) were referrecl to, and thisis the matchiftg device between 50 ohm coaxial line ancl 3cm wave gulde.s116 J. Takahaslti, A. Obuya, T. Oga2uce, and I'. Haslti.   To cl}eck its behavior, we measure(i the voita,5cre stancling xSrave ratio(V. S. i\V. R.) in t'S cm wave gaicie when the ridge type wave gui(iie isinsertecl between 3 cm wave guicle Emcl 50 ohm eoaxial Iine, a•ncJ reasoR-k.ble i'eg.i)lts were obtainecl as shown in [I]able III belox7v. '      TABIJE I. Some restil-ts eoncerning ridge ty}]e wave guide.i Wave meter  sca]e "L"23.68 mmn93.9324.2524.62  ConverterCyystal Current2.50 mA3.505.l24.12 V. S. W. Pv. in3em wave guide331482 .]33g1582 .1Impedance caleulatedfron} V.g. SV. P.•. "Z"698 .P.67i696671The characteristie.x lms.l,tSi.tttxLsNL,g•.g.im}')edance of 3 em wave guicle     Ottt34emtg.•srNlt/tl l•.l'i:•S-Type1•5cmTrapIN23 Silieon Crystal1•5cm Wave Gui(le     A-A SeÅëtion (         &omp.--t:e "" 523 O.gke•-'.I./e•t?-k- Aill nll)l)gftipov-t22•5Nx tiZ.•}/?l2..s.X ' xXxÅ~. xNfi              Fig. 3. gchematie sketeh<3) Atten2sato7' : Vane typea thin bakelite plate eoatetlbinder consi$ting' oÅí poly$tyrene and-ation is about .9.0db.<4) T'Yave oneter: A tyansmi$sionA 3cm Ridge Wave (}uideTrap PosiÅíion Adj uster. •                       '       of f'reguenc)r eonverter.variable attenuator i$ used. The vane isxviSh the mixture ot! graphite powdei' and        benzol solvent. Maximum atÅíenu-''  type eavky wave meter utilizing               15em J•ilave-length 21fiero2va2}e Spectroseopae. ii7TEoii mocle is usecl in 8.5-9.81{dyIelsee range. Mlo suppress [l]`ras(!Iiiimode, behind its pi,stoi} is inserted the lii}k of thin nickel plate w•hichis u$ed because of unavailablenes$ o/ff poiyiron. [l]hi$ wave meter is$elf-calibrating ancl can affrord the frequeney meastn'ement to theaccuracy of -Hi"" 5Me/see.   [Che outpat Åírom the crystal detector attachecl to tlie cavit>r is ledthrough the video amplifler and used as a fre<{iieltcy marker pip o]]the oseiltograph $ereen. . •(5) Orz,fstals: IN23 silieon crystai$ are usecl !"or eonverter and IN26'for detec't!on of 1.5cm wave. X)Ve remove IN26 t'rom the wave guiclefor i'bs ,gafety except in case- of experiment being earrie(i on.(6) Absoption eetg: The absorptioii eell is eonstrueted ft'on] brass eir-calar wave gui<le of .2.9m len.trth, 2.`9J9em iime}' diameter and 1),.t59. cmouter clian]eter. Of comrse, we 1{now that the rectangular wave guideis better for our purpose, btit sin(;e it is noC available Åí'or us imd/er thepreseitt circumstanees, we have empioyecl tlne folloxving proeecliire : 'Ll)heseetion of 1.5cm wave reetangidar gnide is graclually chan.crecl t'romrectas}gle of 1)3.0 mm Å~ 6.5 mm to She eircle of 22.9 nim ( iamete}' thro"ghellipt}ie section tapered along 2`9, cm length. [lrhe sm'faee finishing ofthis taperecl part is most eareful!y done and so expectecl symmeti'y andincon$iclerable reffection i$ attained. .'   The mica winclow of about 1120mm thickiiess is fixecl at each endto seal the cell by means oi' red beeswax and brass ring to clan]p andg,ome cares are tal<en to mi'nimize the }'eflection from these junctionpoints. Bnt we catmot yet suceeed to suppress completeiy sueh refleetion,as some ghosts have appeared which, however, ean be clearly distin-giiished Åírorn ab$orption iiRes.   W'e sitppose that the mode in the eell is mainly [I]Ept but sonie othermodes ean be anticipatec] to oeeur at the sarne time, whieh we are nowplaBning to sup:press.('r') b'a2v-tooth gene7.ato7•: [Irhe saxv-tooth generator of frecluency r'aii.qnvet'rom l.5c/sec to ir50c/see is msed. Its cireuit is similar to that ofA.H.Sharbamgh (5). ILow $weep rates serve to better resolution andto more aceva'ate production of the abso!ption line shape. 50voltsweep vol'tage applied to the refieetor eiecSrocle of klystron suraees tosweep the 100Mclsee band width at 1.5cm wave. ,  'rLI]he sweep frequency is 60elsec when the video amplifier is used,and 2c/sec when the narrow bancl reeeiver is.(8) .bga7'?'ozv ban(l receitter : A handmade single ban(l receiver with cry-stal filter is used. The selection of frequency 463kclsee is niade.forli8 X. Tak'ahashi, A. Okafyct, T. Ogawa, ancl 7'. Hashiiconvenience only. [Vhe gain is about 140clb, tl]e bancl xvidth ean bechtmgecl Åírom 500elsec to 10ke/see on five s#eps, ancl for input stage,low noise tube 6AC7 is useC{.(9) Vi(leo a7?zpliLfie7': The gain is about leOclb. Ilrhe frequencyresponse is snfficient for our purpose.(10) Oseielogo'aph: The type STIOOIA oÅí Matsuda M'fg. Co. is usecl,some acl(/litional measures to adapt f"or, our set bein.cr taken.(11) 'Vaeie2e7?z sz/ste7?z : [I]he blocl< diagram of vaeuum system is shownin Ili"ig. 4. Phillips gauge was useci for measuring pressure oÅí' the gas,sinee it has fai}'ly good sensitivity anc.l moreover is not Epoilecl by.cr,ases. Its n)easuring limit is abont 10--5mmi{IIg.   In o}'cier to obtain greater aecuracy at lower pressure, however,a more sensitive ionization gaurge with l[]. N. Ric]eitour stabiiizatioit eir-ciiit(6) "'as used. 'SL\e have thus obtained the minimuiin pressure asloxv as IO-`'mm}Ig in "'ave .cruide eell. .MicaWindo"2tnragbHoleleoocc.tiOmrn100ec!Omm12mmPhtllipseaue10mmManometer10mmGasTrapllllllIi"th •t/•-:.r/i":AbsorptienCellHic}<manDiffusionPumP-t"- t----mShiraazuD5A-1RetaryPumpSa,n,pleTraptOMtr115ramIonixationGauel'CencoKighVacuumPumpMicaWinapwi5mm                Fig. 4. Block diagram of vaeuttm systen].        '                         '3. Absorption spectra ef methyl bromide   XVith otir mierowave speetroseope, we observecl the rot.ktionai tran-sitioi} tJ' , .Zis"(O, O)-el',K(l, O) oÅí C}I3Brve ancl Cl}IsBi""i. [l]he absorptionfreqtiencies were rneasured with the cyiin(']rieal c.revity wave nieter ope-rating. in TEoii mocie. rrhe ref onant l'requencies are given ,by the f'ollow-in.cr' forniula: f=: (c12) L'"(7.663417rP)L' + (1/L)L']S, '                                          A               1.5 em VVave-length ]ficrotvave SpaectToscope. 119xxrhere c is the light velocity, and D and L are the diameter ancl lengthof tl}e eyiinder respeetively.    Our measurir}g system can afforcl the aecuracy of Å} 5 Mc/sec at 3 cmwave. [lrhe satellite structure of rotationai line of CHeBr is cause6iby the interaction ot' nuelear quaclrupole moment of Br with moieeularfield. The theoretical formlila for t•he interaction (7, 8, 9, 10) is    Eo --- ee /tl.l;(,,,l}t2 ,, - i) Bat ,a,'SO,, li 'S, 7,,,i `iil ?, Sl,S`• "rm ",," ,               '                                                   '               ''xxritl}             C == Y(rv + 1) - I(J + 1) - ,J(,J + 1) ,             .F =J+ J, J+1- 1, •-•-- ,V- fl,wl}ere 1 is the spin oÅí the interacting nuelelis, e the eleetroni6 eharge,Q the nuelear quadrupole moment, and a2YIO:-2 is the divergence alongthe molecular axis of the moleeular field at the interacting nucieus.   [liior the case of CK3Br, we performed caleulationg., b'y putting thefoliowing values (15)              '                   '              ee 02VlO:-2 -- 577.3 Me!see for CH;s Br79 ,                         -h 4S`9J.4 Me/sec for CH3Brgi ,                      1 -ww 3!2 for both BrS"and BrS',ancl using selection i'uies •               A,J =+1, AK -- O, AF -- O, Å}1.   Omr observecl values ancl ealelilated values are summarize(il. in Ta-ble l[I.            TABLE II. Absorption frequencies of CH3Br.CH3Br79ye " 19197Mc/secCH,BrSivo == 19064 Mc/secTransitionF =3/2.Y2   3/2-3 2   3/2-5/23f2->Y23/.9-3/23/2->5/2Frequeney (obs.)1899sMc/secl926,191e,1896o19!7o1906si Frequency(caic•) l         i18992 Me/sec1925219108l1894319i60190"OI(b'e: frequenCy of the unsplit rotational line)120 J. Tqhaha•slii, A. Ohaya, T. Ogct2ua, and T. Hashi.The calculated and observed values agree well with each other withinthe error of our present frequency measuring system, whose accuracyis Å} 10 Mc/see at 1.5 cm wave.   Several accurate measurements for CH3Br have been already report-ecl (11, 12, 13, 14, 15). Among them, however, 1.5 cm wave-length spee-trum was observed only by A. H. Sharbaugh and J. Mattern (15).   Two absorption Iines accompanied by one ghost are shown in Fig. 5.                l ;4              ghost . 18994Mc/sec 1896oMe/sec                            CH3Br79 OH.aBr8'                          F = 3/2-1/2 312-.1/2                 Fig. 5. The absorption lines of CH3Br..   The intensity comparison among absorption lines was not made thistime, because it was diMeult to adjust all circuit components for eachline into the same conditions, especially so fdr the lines lying in the•different eleetronic tuning ranges of klystron, and further the outpntpower of klystroll eould not be kept constant without any •necessary'procedure over the range of electronic tuning.   [I]he mo.'te accurate frequency measuring system utilizing harmonics-of 100 kclsee crystal controlled oscillator which makes zero beat .Nviththe standard wave of the Standard Frequency Station JJY is nowunder construction by us.4. Acknowledgements .   The authors express their heartfelt thanks to Prof. R. Nozu, Dr. R.Goto, and Mr. H. Shakutsui for the preparation of the sample, and4             ZoYem l!ravc-lenatlt alficro2vctve Speei.roscope. 121                          '                                                          'xve owe deep thanks to IDr. 0. Cary who helpecl lis to get klyst}ron andsiilcon crystals. -41so, mach eredit 2s due to .TMessrs. }I. Narumi andH. [l]akeyania ancl several men]bers both in Arakatsu IJaboratory anc.l inour Laborato}'y. XVe thank Åíurkhey to Meg, sr's. ID. IblTJakayama ancl K.I[wat.a for their eooperatioz} in construe'bing wave meter and otl]ercomponents Rsed in our re:heareh.igig,  1i'                    RE.Yilfll;Nl,B]NCE$VvT. Gorcly, P.ev. Mod. Phys., 2g (1948), 66S.g. B. Cohn, ?roc I. rfo.E;, 35 (!947), 783.T. G. A[ihran, IProe. L R. E., 37 (l949), 640.C. GF. IANIontgomery, Technig2te of ]tici'oieave Bieaszu'ement& rtiad. Lab. Series ll, (i"}le- (Straw-I{ill, 1947), 322. 'A. I-I. Sharbaugh, B•.S.I., 21 (1950), 120.IJ. ]bl. R•idenour, and C. W. Lam})sbn, Yv.S. I., 8 (l937), 162. .I'I. B. (l. Cashnir, On tlte interaction between Aio?nie iVuclei ancl Electrons (k'eyler's [I]weede (}Tlenootsehap, E. F. Bohn, Jl aalent, 193o"); IPhysica, 2 (i935), 719.D. K. Coles, and SV. E. Good, P' hys. Bev. 7e (1946), 979.tJ. I'I. Van Vlecl<, Phys. Rev., 7! (1947), 468.B. IP. Dailey, R. L. Kyhl. .XI. W. IP. gtrtmdberg, J. Iml. VanVleek, ancl E. B. "'i}$on. Jr., Ph>'s. Pvev., 7e (1946), 9S4.W. D. I{ers}xberger, J. Appl. ?hys., Z7 <1946), 495.Xl7. Gordy, J. XV.Simons, and A. G.Smit.h, Pk.vs. Rev., 72 (1947), 249, 344.tJ. NX7. S!mons, W. Gordy, and A. G. Smith, Bul}. ATner. Phys. Soe., 23 (i948), INo.3.W. Gordy, J. Sl T. Simons, and A. Gx.Stnid}, IPhys. IRev., 74 (1948), 243.A. I'I. Sharbaugh. and J. Ivlattern, Phys. ?boev., 75 (1949), 1102.'

1.5 cm Wave-length Microwave Spectroscope

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1.5 cm Wave-length Microwave Spectroscope

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