eBook Here Vn 12 Ly Thuyet Hat Nhan Nguyen Tu 140 Cautn 7756

Embed Size (px)

Text of eBook Here Vn 12 Ly Thuyet Hat Nhan Nguyen Tu 140 Cautn 7756

Phn Ht nhn nguyn tBin son Nguyn Thanh H - 0972 64 17 64 - 1 - ChngHT NHN NGUYN T I.TNH CHT V CU TO HT NHN 1. Cu to ht nhn - Ht nhn tch in dngbng +Ze (Z l s th t ca nguyn t trong bng tun hon), kch thc ht nhn rt nh, nh hn kch thc nguyn t khong 104 105 ln - Ht nhn c to thnh bi hai loi ht l prtn v ntrn; hai loi ht ny gi chung l nucln. oPrtn, k hiu p, mang mt in tch nguyn t dng +e, khi lng 1,67262.10-27kg. oNtrn, k hiu n, khng mang in, khi lng 1,67493.10-27kg. oHt nhn nguyn tcha Z prtn v N ntrn. Tng s nucln trong ht nhn A = Z + N, A gi l s khi. - K hiu ht nhn: Ngi ta dng k hiu ha hc X ca nguyn t t tn cho ht nhn:XAZ hoc AX hoc XA. V d: Ht nhn Na c th k hiu bng cc cch sau: , hay,23 2311Na Na hoc Na23. - ng v oCc ht nhn ng v l nhng ht nhn c cng s prtn Z nhng c s ntrn N khc nhau, do c s khi A = Z + N khc nhau (c cng mt v tr trong bng h thng tun hon). V d:H11D H2121hayT H3131hayo Hyr c ba ng v l: + Hyr thngH11 chim 99,9% hyr thin nhin. +Hyr nng hay triD H2121hay chim 0,015% hyr thin nhin. +Hyr siu nng hay tritiT H3131hayht nhn ny khng bn, thi gian sng ca n khong 10 nm. oCacbon c nhiu ng v, trong ch c hai ng v bn lC126 vC136. Trong mt khi cacbon t nhin bn vng,C126 chim khong 98,89% vC136 chim khong 1,11%. - ng v phng x l ng v m cc ht nhn ca n c th phng ra cc tia phng x v bin i ht nhn ca nguyn t khc. V d: ng vTh He U234904223892+ 2. Khi lng ht nhn - Cc ht nhn c khi lng rt ln so vi khi lng ca electron; v vy khi lng nguyn t tp trung gn nh ton b ht nhn. tin cho tnh ton khi lng ht nhn, ngi ta nh ngha mt n v mi khi lng c khi lngcc ht nhn. n v ny gi l n v khi lng nguyn t, k hiu l u. - n v khi lng nguyn t u c gi tr bng 1/12 khi lng nguyn t ca ng vC126, v vy cn gi l n v cacbon. kg u272310 . 66055 , 110 . 023 , 6012 , 0.1211= =- Khi lng v nng lng oTheo h thc Anh-xtanh v mi quan h gia nng lng E v khi lng m ca cng mt vt c dng: E = mc2 oNng lng tnh ra n v eV tng ng vi khi lng 1u l:E = uc2 ~ 931,5 MeV=>1u ~ 931,5 MeV/c2 (MeV/c2 cng c coi l n v o khi lng ht nhn) oCh : L thuyt Anh-xtanh, mt vt c khi lng ngh m0 (khi lng ca vt trng thi ngh), khi chuyn ng vi tc v, khi lng s tng ln thnh m (khi lng ng) vi2201cvmm=Khi nng lng ca vt (nng lng ton phn) lE = mc2 = 22201cvc m Nng lng E0 = m0c2 c gi l nng lng ngh v hiu s E E0 = (m - m0)c2 chnh l ng nng ca vt. II.NNG LNG LIN KT CA HT NHN. PHN NG HT NHN 1. Lc ht nhn - Cc nucln trong ht nhn ht nhau bng cc lc rt mnh to nn ht nhn bn vng. Cc lc ht gi l lc ht nhn. - Lc ht nhn khng phi l lc tnh in v lc ht nhn lun l lc ht gia hai prtn, gia hai ntron v gia mt ntron vi mt prtn. Lc ht nhn khng ph thuc vo in tch. - Lc ht nhn khng cngbn cht vi lc tnh in hay lc hp dn; n l mt loi lc truyn tng tc gia cc nucln trong ht nhn. Lc ny cng c gi l lc tng tc mnh, nhng ch tc dng khi khong cch gia hai nucln bng hoc nh hn kch thc ca ht nhn. 2. Nng lng lin kt ca ht nhn - Khi lng ca mt ht nhn lun nh hn tng khi lng ca cc nucln to thnh ht nhn . - chnh lch gia hai khi lng c gi l ht khi ca ht nhn, k hiu Am:Am = Zmp + (A - Z)mn - mx Trong :Am l ht khiZmp l khi lng ca Z prtn (A Z)mn l khi lng ca (A - Z) ntronmx l khi lng ca ht nhn X Phn Ht nhn nguyn tBin son Nguyn Thanh H - 0972 64 17 64 - 2 - - Nng lng lin kt ca mt ht nhn c tnh bng tch ca ht khi ca ht nhn vi tha s c2. Wlk = [Zmp + (A Z)mn mx]c2 Hay Wlk = Amc2 - Nng lng lin kt ring (k hiu AWlk) l nng lng lin kt tnh cho mt nucln. Ht nhn c nng lng lin kt ring cng ln, th cng bn vng. 3. Phn ng ht nhn - Phn loi: Phn ng ht nhn thng chia lm hai loi: + Phn ng t pht l qu trnh phn r ca mt ht nhn khng bn vng thnh cc ht nhn khc. + Phn ng ht nhn kch thch l qu trnh cc ht nhn tng tc vi nhau to thnh cc ht nhn khc. - c tnh ca phn ng ht nhn: + Bin i cc ht nhn. + Bin i cc nguyn t.+ Khng bo ton khi lng ngh. - Cc nh lut bo ton trong phn ng ht nhn oBo ton in tch: Tng in tch ca cc ht tham gia phn ng bng tng in tch ca cc ht to thnh sau phn ng.(A B C DZ Z Z Z + = + ) oBo ton s nucln (bo ton s A): Prtn c th bin thnh ntrn v ngc li nhng s nucln l khng i. (A B C DA A A A + = + ) oBo ton nng lng ton phn: Tng nng lng ca mt h kn c bo ton.( ) ( ) ( ) ( )A A B B C C D DE E E E E E E E + + + = + + +oBo ton ng lng: ng lng ca mt h kn c bo ton. A B C Dp p p p + = + - Nng lng phn ng ht nhn:Gi tng khi lng cc ht nhn trc phn ng l mtrc, tng khi lng cc ht nhn sau phn ng l msau + Phn ng ta nng lng khi mtrc > msau, nng lng ta ra c tnh bng cng thc:Wta = W = (mtrc msau)c2 + Phn ng thu nng lng khi mtrc < msau, nng lng thu c tnh bng cng thc:Wthu = |W| = -W III.PHNG X 1. Hin tng phng x - N: Phng x l qu trnh phn hy t pht ca mt ht nhn khng bn vng (t nhin hay nhn to). Qu trnh phn hy ny km theos to ra cc ht v c th km theo s pht ra cc bc x in t. Ht nhn t phn hy gi l ht nhn m, ht nhn c to thnh sau phn hy gi l ht nhn con. - Cc dng phng x+ Phng x o Ht nhn m X phn r to thnh ht nhn con Y, ng thi pht ra tia phng x o theo phn ng sau: He Y XAZAZ4242+ hay c th vit He XAZAZ42 o *Bn cht l chm ht nhn hli He42 gi l ht o. * Tnh cht: mang in tch (+2e) nn tia o lch v bn cc m ca t in. Ht o phng ra vi vn tc v ~ 107m/s, lm ion ha mi trng v mt dn nng lng, vvy n ch i c ti a trong khng kh 8cmv kh nng mxuyn yu. + Phng x |- Phng x |- l qu trnh pht ra tia |-. Tia |- l cc dng electron ( e01 ). Dng tng qut ca qu trnh phng x:Y XAZAZ 1 + | + Phng x |+ l qu trnh pht ratia |+.Tia|- l cc dng pzitron ( e01). Pzitron ( e01)c in tch +evc khi lng bng khi lng electron, n l phn ht ca electron. Dng tng qut ca qu trnh phng x:Y XAZAZ 1 +| + Tnh cht: Cc ht | phng ra vi vn tc v ~ c = 3.108m/s, cng lm ion ha mi trng nhng yu hn tia onn tia | c th i xa hng trm mt trong khng kh v kh nng m xuyn mnh hn tia o. + Phng x * Bn cht: l sng in t c bc sng ngn ( < 0,01nm), ng thi l chm phtn c nng lng cao. *Tnhcht: tiackh nngmxuynrtln,cthiqualpchdyhngchccmvgy nguyhimchocon ngi, v khng mang in nn n khng b lch trong in trng v t trng. 2. nh lut phng x - c tnh ca qu trnh phng x + C bn cht l qu trnh bin i ht nhn+ C tnh t pht v khng iu khin c+ L mt qu trnh ngu nhin - nh lut phng x + Xt mt mu p.x c N h.nhn ti thi im t. Ti thi im (t + dt) s h.nhn gim i v tr thnh (N +dN) vi dN < 0. + S ht nhn phn hy trong khong thi gian dt l (-dN)-dN = Ndt Trong l mt hng s dng gi l hng s phng xdtNdN =+ Gi N0 l s ht nhn ca mu phng x tn ti lc t = 0, s ht nhn N vo thi im t > 0 l:N = N0te Phn Ht nhn nguyn tBin son Nguyn Thanh H - 0972 64 17 64 - 3 - - Chu k bn r: Mi chtphng x c c trng bi mt thi gian T gi l chu k bn r, c sau mi chu kny th s nguyn t ca cht y bin i thnh cht khc. 693 , 0 2 ln= = T3. ng v phng x nhn to - Ngoi cc ng v p.x c sn trong t nhin, ngi ta ch to c nhiu ng v p.x gi l ng v p.x nhn to. - Phng x nhn to v phng php nguyn t nh du + Bng phng php to ra phng x nhn to, ngi ta to ra cc ht nhn phng x ca cc nguyn t X bnh thng, khng phi l to ra cht phng x theo s tng qut sau:X n XAZAZ1 10+ ++ XAZ1 +lccngvphngxcaX.Khitrnlncchtnhnbnhthngkhngphngx,cchtnhnphngx XAZ1 +cgilccnguyntnhdu,chophptakhoststnti,sphnb,schuynvncanguyntX. Phng php nguyn t nh du c nhiu ng dng trong sinh hc, ha hc, y hc ... - ng v 14C, ng h Tri t + tng cao kh quyn, trong thnh phn ca tia v tr c cc ntron chm (tc vo c vi tram mt trn giy). Mt ntron chm khi gp ht nhnN147(c trong kh quyn) to nn phn ng: p C N n1114714710+ +C146 l mt ng v phng x |-, chu k bn r 5 730 nm. + Trong kh quyn c ccbon ioxit: Trong cc hnhn cacbon y c ln cC126 vC146(t l khng i:C146chim 10-6 %) + Cc loi thcvt hpth CO2trongkhngkh, trong cacbon thng v cacbon phng x vi tl 10-6%. Khi loi thc vtycht, khngcn s hp th CO2 trong khngkhvC146khngcn tisinhtrongthcvtna.VC146 phng x nn lngC146 gim dn trong thc vt . So snh cc t l cho php ta xc nh thi gian t lc loi thc vt cht n nay. Phng php ny cho php tnh cc khong thi gian t 5 n 55 th k. IV.PHN NG PHN HCH 1. C ch ca phn ng phn hch - Phn ng phn hch l g ? Phn hch l phn ng trong mt ht nhn nng v thnh hai mnh nh hn. - Phn ng phn hch kch thch. + Xt cc phn ng phn hch ca cc ht nhn:U23592,U23892,Pu23994 v l nhng nguyn liu c bn ca cng nghip nng lng ht nhn. + truyn nnglngkch hot cho ht nhn X l cho mt ntron bnvo X X bt ntron . Khibtntron, ht nhn X chuyn sang mt trng thi kch thch, k hiu X*. Trng thi ny khng bn vng v kt qu xy ra phn hch. n + X X* Y + Z + kn(k = 1, 2, 3) + Ht nhn X* v thnh hai mnh km theo mt vi ntron pht ra. + Qu trnh phn hch ca X khng trc tip m phi qua trng thi kch thch X*. 2. Nng lng phn hch - Xt cc phn ng phn hchU23592 sau y: n I Y U U n10138539539* 2369223592103 + + +n Sr Xe U U n10953813954* 2369223592102 + + +- Phn ng phn hch ta nng lng + Cc php tnh ton chng t phn ng phn hch trn l phn ng ta nng lng, nlng gi l nng lng phn hch + V d: S phn hch ca 1g 235U gii phng mt nng lngbng 8,5.1010J, tng ng vi nng lng va 8,5 tn than hoc 2 tn du ta ra khi chy ht. - Phn ng phn hch dy chuyn. + Saumi ln phn hch, c k ntron c giiphngn kch thch cc ht nhn 235Ukhc tonn nhng phnhch mi. Sau n ln phn hch lin tip, s ntron gii phng l kn v kch thch kn phn hch mi. + Khi k < 1 phn ng phn hch dy chuyn tt nhanh. + Khi k = 1 phn ng phn hch dy chuyn t duy tr v nng lng pht ra khng i theo thi gian. + Khi k > 1 phn ng phn hch dy chuyn t duy tr v nng lng pht ra tng nhanh v c th gy nn bng n. + Mun cho k > 1, khi lngca cht phn hchphi ln s ntron b bt nh hn nhiu so nhiu so vi s ntron c gii phng. + Khi lng ti thiu ca cht phn hch phn ng phn hch dy chuyn duy tr c trong gi l khi lng ti hn. 3. Phn ng phn hch c iu khin - Phn ng phn hch ny c thc hin trong cc l phn ng ht nhn, tng ng vi trng hp k = 1. - m bo cho k = 1, ngi ta dng nhng thanh iu khin c cha bo hoc caimi. - V bo hoc caimi c tc dng hp th ntron nn khi s ntron tng qu nhiu ngi ta cho cc thanh iu khin ngp su vo trong l hp th ntron tha. Nhin liu phn hch trong cc l phn ng thng l 235U hay 239Pu. - Nng lng ta ra trong l phn ng khng i theo thi gian. V.PHN NG NHIT HCH. 1. C ch ca phn ng nhit hch - Phn ng nhit hch l phn ng trong hai hay nhiu ht nhn nh tng hp li thnh mt ht nhn nng hn. - iu kin thc hin Phn Ht nhn nguyn tBin son Nguyn Thanh H - 0972 64 17 64 - 4 - + Nhit cao (50 100 triu ) chuyn hn hp nhin liu sang trng thi plasma. + Mt ht nhn trong plasm