Qhov kev ruaj ntseg ntawm lub ntsiab lus txhais tau tias lub zog tsis hloov nws tus kheej ntawm cov protons, neutrons thiab cov yam ntxwv yooj yim. Raws li kev ruaj khov ntawm lub keeb, nws muaj peev xwm raug faib ua ob hom: ruaj khov nuclei thiab tsis ruaj khov (los yog xov tooj cua) nuclei.
1. Atomic nuclei nrog ib tug xov tooj ntawm cov protons sib npaug thiab ntau dua 84 tsis ruaj khov. Ntawd yog, cov khoom tom qab atomic number 84 yog tag nrho cov khoom siv hluav taws xob.
2. Lub nucleus nrog tsawg dua 84 protons muaj txawm tias muaj pes tsawg tus protons thiab neutrons, thiab nws cov nucleus ruaj khov.
3. Cov pob hluav taws xob tsawg tsawg nrog cov protons lossis neutrons sib npaug ntawm 2, 8, 20, 28, 50, 82, 126 yog qhov ruaj khov tshwj xeeb. Cov naj npawb no yog hu ua cov lej ua khawv koob. Tag nrho ob qho ntawm cov protons thiab tus naj npawb ntawm neutrons yog cov lej khawv koob, hu ua ob npaug tooj tus naj npawb nuclei.
4. Qhov piv ntawm cov naj npawb ntawm neutrons rau cov naj npawb ntawm protons yog n / p. Thaum Z< 20,="" n="" p="1," thiab="" lub="" nucleus="" ruaj="" khov.="" raws="" li="" tus="" nqi="" hluav="" taws="" xob="" atomic="" nce,="" tus="" nqi="" ntawm="" n="" p="" nce,="" thiab="" qhov="" loj="" piv="" piv,="" ntau="" dua="" qhov="" kev="" ruaj="">
Nuclear kab noj
Tsis ruaj khov hluav taws xob atomic nuclei yuav nquag ua hloov pauv mus rau lwm lub hauv paus thaum emitting hluav taws xob. Qhov kev hloov pauv no yog hu ua hluav taws xob xeb. Muaj peb hom duab hluav taws xob tso tawm los ntawm lub pob hluav taws xob thaum lub sij hawm ua kev lwj: xoo, β duab ci thiab γ duab ci.
Alpha rays yog alpha particle ntws, uas zoo them helium nuclei. Beta rays yog cov kwj tawm ntawm kev txav nrawm ntawm hluav taws xob.
Nws muaj ob hom β lwj: β + thiab β-. Thaum ays txiav tawm, ntxiv rau cov positrons lossis cov xaim hluav taws xob tsis zoo, neutrinos lossis antineutrinos kuj tawm. Beta-decay yog qhov kev hloov pauv ntawm neutrons hauv lub nucleus mus rau protons (tshuav nyob hauv lub nucleus) thiab tso tawm cov xaim hluav taws xob thiab antineutrino cuam tshuam nrog xaim hluav taws xob. Beta + lwj yog qhov tseeb tias muaj tsawg dua ntawm neutron nyob rau hauv lub nucleus, thiab protons tau hloov pauv mus rau hauv neutrons (tseem tshuav nyob hauv nucleus), thiab positron thiab neutrino raug tso tawm tib lub sijhawm.
Gamma rays yog kwj ntawm photons. Nws feem ntau tawm thaum lub zog tshiab tsim tom qab alpha lwj los yog beta lwj. Qhov no yog vim hais tias lub xov tooj cua leej niam lub zog ua lub hauv paus zoo siab tus ntxhais nucleus tom qab hais txog kev lwj, thiab thaum tus ntxhais nucleus hloov mus rau lub xeev ib txwm, nws feem ntau radiates gamma photons.
Tus lej ntawm tag nrho cov nqi thiab qhov ntau ntawm tag nrho cov khoom ua ntej ua kom lwj yog sib npaug rau tag nrho cov nqi thiab tag nrho qhov loj ntawm txhua qhov khoom tom qab hniav lwj
Kev cai lij choj ntawm cov nyom hluav taws xob tsis zoo
Muaj N nuclei nyob hauv tus qauv ntawm lub sijhawm t, thiab dN decays tsis pub dhau lub sijhawm.
t=0, N=N0, yog
Cov txheej txheem saum toj no yog hu ua kev cai lij choj ntawm cov xov tooj hluav taws xob tsis zoo.
Lub ntsiab lus ntawm lub cev yog: lub sijhawm t, qhov sib piv ntawm tus naj npawb ntawm nuclei uas lwj ntawm ib ntu ntsuas rau tag nrho ntawm nuclei ntawm lub sijhawm ntawd. Qhov loj dua, qhov nrawm dua tuaj.
Nws yog txoj kev siv ib nrab-lub neej los cim qhov tus nqi ntawm lwj ntawm radioactive ntsiab. Lub ntsiab lus ntawm ib nrab-lub neej yog: lub sij hawm xav kom tus nucleus yuav lwj mus rau N=N0 / 2. Qhia los ntawm T.
Qee lub sij hawm nruab nrab lub neej τ tseem siv tau los qhia txog kev nrawm ntawm lwj. Qhov nruab nrab ntawm lub neej yog hais txog tus nqi nruab nrab ntawm lub sijhawm uas txhua lub nucleus muaj ua ntej nws txiav tawm.
Radioactivity (tseem hu ua radioactivity) yog hais txog cov xov tooj ntawm kev tawm tsam ntawm lub xov tooj hluav taws xob nyob rau ib lub sijhawm.
Hauv Cov Txheej Txheem Hauv Tebchaws Thoob Ntiaj Teb, chav ntsuas ntawm kev ua haujlwm yog becquerel (Bq). 1Bq sawv cev rau kev ua haujlwm ntawm lub chaw tsim hluav taws xob uas dhau mus rau hauv kev nthuav dav nuclear ib zaug ib zaug. Feem ntau ntawm chav nyob yog Curie (Ci).