1、HPGe 丫譜儀系統死時間校正方法的實驗研究四號黑體，加粗，居中，段前0、行，段后1行。摘要給出了HPGe譜儀系統死時間校正的一種實用方法。用強源干擾找到了HPGe飛譜儀系統百分死時間與計數率丟失校正因子的關系，使該系統允許計數率大大提高,ExperimentalstudyonthemethodofdeadtimecorrectionForHPGespectrometersystem小三號字，ArialBlack,居中，段前1.5行，段后1.5行。標題兩行間距30磅ApracticalmethodofdeadtimecorrectionforHPGespectrometersystemwasg

2、iven.TherelationbetweenthepercentdeadtimeandthecorrectionofcountingratelossesforHPGespectrometersystemwasfoundbyusingastrongsource.Therefore,theactivitymeasurementcanbefinishedatveryhighcount注意：如果摘要內容較多，一頁排不下，則中文摘要（含關鍵詞）單獨占一頁，英文摘要（含關鍵詞）單獨占一頁。如下所示：平頂從而解決了放射性定量測量中的一些困難。關鍵詞：HPGe珊儀，死時間，校正因子小四號黑體，加粗小四方木體

3、/TimesNewRoman小四號宋體/TimesNewRoman,1.5倍行品巨。小二號黑體，加粗，居中，I段前1.5行,段后1.5行JAbstractrate,withthisspectrometer.TimesNewRoman,1.5KeyWords:HPGespectrometer,Deadtime,小四號字，ArialBlack小四號字，Times、NewRoman四號字，ArialBlack，居中,段前0行，段后1行。小四方子,英文狀態下的逗號，且后有一空格倍行距（如果內容較多可適當減速小行距，以美觀為標準）oefficientofcorrectiona-取代甲苯定向硝化的理論研究

4、摘要運用密度泛函理論(DFT),研究了吸電子氟基和供電子羥基在取代甲苯的a-H以后，其鄰、間、對各位次進行硝化反應的速控步驟,在B3LYP/6-311G*水平上，計算了該速控步驟基元反應各反應駐點(反應物、過渡態和中間體)的優化幾何、電子結構和能量性質，并首次給出了目標硝化反應速控步驟的IR譜學的動態特征及解析，從微觀層面上驗證了反應坐標CN的形成和CH的斷裂是非協同的，從而無一級動力學同位素效應的實驗事實.通過對目標硝化反應速控步驟的微觀動態計算，驗證了氟基對甲基定位的影響.氟基的電負性大，吸電子能力強，取代甲苯的為H以后對硝酰陽離子的進攻有抑制作用，活化能較取代前高，但比較甲基氟各位次硝化

5、活化能的相對大小得知，一CH2F仍為鄰、對位定向基團.而供電子羥基取代甲苯的a-H以后，則對硝酰陽離子的進攻有促進作用，因而各反應駐點絡合物的穩定化能較a-H取代前甲苯的有所增大，且鄰、對位硝化的活化能較間位低，故CH20H為鄰、對位定位基.但對位因硝化活化能低，反應放熱多，空間位阻小，為親電試劑NO+最有利的進攻位；而鄰位則因羥基取代甲苯mH后多了2一個氧原子，增大了鄰位進攻的空間位阻，使得其絡合物的能量比相應對位的高.關鍵詞：葦基氟，甲醇，e 取代，取代基效應，速控步驟TheoreticalStudyonSelectivityforNitrationofa-SubstitutedTolue

6、newithNitroniumAbstractTherate-determiningstepsofisomericortho,metaandparanitrationsofbenzylalcoholandbenzylfluoridehavebeentheoreticallyinvestigatedatB3LYP/6-311G*level.Stationarypointsofthestepinvolvingreactant,transitionstateandintermediatecomplexesweresuccessfullylocatedandcharacterizedwithoutan

7、yrestrictionontheinternalcoordinates.Theirmoleculargeometries,electronicstructures,IRspectra,andtheFMOsymmetriesoftwoinitialaromaticcompoundsandthenitroniumionNO2havebeenstudied.ThevibrationalshiftsofCNandCHstretchesfromTStoINTattherate-determiningstepoftargetaromaticnitrationsshowupthattheformation

8、ofC-NandthecleavageofCHarenotcon-cernedbutstepwisetoprovideanexplanation,onamicroscopicscale,fortheexperimentalfactoftheabsenceofkineticisotopiceffectinthenitrationprocessforthefirsttime.Also,theinfluenceofintroducedfluorineontheorientationeffectwasfiguredbycalculatingthemicroscopicandkineticpropert

9、iesoftherate-determiningstepofconcernedaromaticnitrations.TheNO2attacktothebenzylfluoridewasdeactivatedbecauseofhighelectronegativityandstrongelectronwithdrawaloffluorineatom.Theactivationenergyafter-substitutionofmethylgroupbyafluorineatombecamehigher.YettheCH2Fgroupwasstillanortho-paradirective,si

10、ncetheactivationenergiesoforthoandparanitrationswererelativelylowerthanthatofmetanitration.Contrarily,theintroductionofelectron-donatingsubstituentOHontothemethylacceleratedtheNO2attack.Consequentlythestabilizationenergiesofcomplexesweredropedevenlowerthanbeforetheo-substitutionoccurred.Theactivatio

11、nenergiesoforthoandparanitrations,however,werealsoquitelowerthantheenergyofmetanitration.Therefore,theCH20Hisanortho-paradirectinggroup.Comparedtotheortho,theparapositionisthemostfavorableduetotheNO2toapproach,foritslowsterichindranceeffectandhighexothermicity.Attackatortho,however,becameevenmorecrowdsinceonemoreOatomhasbeenintroducedaftertheo-substitutionontothemeth