Txhim emission yog cov txheej txheem los ntawm cov photon nkag ntawm qee zaus tuaj yeem cuam tshuam nrog lub zog atomic electron (los yog lwm lub xeev zoo siab molecular), ua rau nws poob rau qis zog. Lub zog tso tawm yog hloov mus rau hauv electromagnetic teb, tsim ib tug tshiab photon nrog ib theem, zaus, polarization thiab kev taw qhia ntawm cov lus tsa suab uas zoo tib yam rau photons ntawm qhov xwm txheej yoj. Thiab qhov no tshwm sim nyob rau hauv sib piv rau spontaneous hluav taws xob, uas ua hauj lwm nyob rau hauv random lub sij hawm, tsis tau mus rau hauv tus account lub puag ncig electromagnetic teb.
Cov xwm txheej kom tau txais kev tawm dag zog
Cov txheej txheem zoo ib yam hauv daim ntawv rau atomic absorption, uas lub zog ntawm cov photon absorbed ua rau ib qho zoo tib yam tab sis opposite atomic hloov: los ntawm qis mus rauqib zog siab dua. Nyob rau hauv ib txwm ib puag ncig nyob rau hauv thermal equilibrium, nqus tau tshaj stimuled emissions vim hais tias muaj ntau electrons nyob rau hauv qis zog xeev tshaj nyob rau hauv siab zog xeev.
Txawm li cas los xij, thaum cov pej xeem inversion tam sim no, tus nqi ntawm kev tawm dag zog ntau tshaj qhov kev nqus tau thiab cov ntshiab optical amplification tuaj yeem ua tiav. Xws li qhov nruab nrab amplifying, nrog rau qhov kho qhov muag resonator, tsim lub hauv paus ntawm laser lossis maser. Tsis muaj cov tswv yim tawm tswv yim, laser amplifiers thiab superluminescent qhov chaw kuj ua haujlwm raws li kev txhawb nqa emission.
Dab tsi yog lub ntsiab lus tseem ceeb rau kom tau txais kev tawm dag zog?
Electrons thiab lawv cov kev cuam tshuam nrog electromagnetic teb yog qhov tseem ceeb hauv peb txoj kev nkag siab ntawm chemistry thiab physics. Nyob rau hauv lub classical saib, lub zog ntawm ib tug electron revolving nyob ib ncig ntawm lub atomic nucleus yog ntau dua rau orbits deb ntawm lub atomic nucleus.
Thaum ib qho hluav taws xob nqus lub teeb lub zog (photons) lossis lub zog hluav taws xob (phonons), nws tau txais qhov xwm txheej quantum ntawm lub zog. Tab sis kev hloov pauv tsuas yog tso cai nyob nruab nrab ntawm lub zog sib cais, xws li ob qho hauv qab no. Qhov no ua rau emissions thiab nqus kab.
Zoo nam
Tom ntej no, peb yuav tham txog lub ntsiab mob kom tau txais hluav taws xob induced. Thaum ib qho hluav taws xob zoo siab los ntawm qis dua mus rau qib siab zog, nws tsis zoo li yuav nyob li ntawd mus ib txhis. Ib qho hluav taws xob hauv lub xeev zoo siab tuaj yeem lwj mus rau qis dualub zog lub xeev uas tsis nyob, raws li ib tug tej lub sij hawm tas li characterizing no kev hloov.
Thaum xws li electron decays yam tsis muaj kev cuam tshuam sab nraud, emitting ib photon, qhov no yog hu ua spontaneous emission. Cov theem thiab cov kev taw qhia cuam tshuam nrog lub emission photon yog random. Yog li, cov khoom siv nrog ntau cov atoms hauv lub xeev zoo siab yuav ua rau muaj hluav taws xob uas muaj qhov nqaim spectrum (nyob ib puag ncig ntawm ib lub teeb ntawm lub teeb), tab sis tus neeg photons yuav tsis muaj kev sib raug zoo rau theem thiab tseem yuav tawm hauv cov lus qhia random. Qhov no yog cov txheej txheem ntawm fluorescence thiab tshav kub tiam.
Sab nraud electromagnetic teb ntawm qhov zaus cuam tshuam nrog kev hloov pauv tuaj yeem cuam tshuam rau quantum mechanical xeev ntawm lub atom yam tsis muaj kev nqus. Thaum ib qho hluav taws xob hauv ib qho atom ua rau kev hloov pauv ntawm ob lub xeev nyob ruaj khov (tsis muaj qhov twg qhia qhov chaw dipole), nws nkag mus rau hauv lub xeev kev hloov pauv uas muaj dipole teb thiab ua zoo li lub zog me me dipole uas oscillates ntawm tus yam ntxwv zaus.
Nyob rau hauv cov lus teb rau ib qho hluav taws xob sab nraud ntawm qhov zaus no, qhov tshwm sim ntawm kev hloov hluav taws xob mus rau lub xeev no nce ntau. Yog li, tus nqi ntawm kev hloov pauv ntawm ob lub xeev nyob ruaj khov tshaj qhov loj ntawm spontaneous emission. Kev hloov pauv ntawm qhov siab dua mus rau lub xeev qis zog tsim ib qho ntxiv photon nrog tib theem thiab kev taw qhia raws li qhov xwm txheej photon. Qhov no yog qhov yuam kev emission.
Qhib
Txhim emission yog Einstein txoj kev tshawb pom nyob rau hauv lub qub quantum txoj kev xav, nyob rau hauv uas hluav taws xob tau piav nyob rau hauv cov nqe lus ntawm photons, uas yog quanta ntawm lub electromagnetic teb. Cov hluav taws xob zoo li no tuaj yeem tshwm sim hauv cov qauv qub yam tsis siv photons lossis quantum mechanics.
Kev tawm dag zog tuaj yeem ua qauv ua lej muab ib qho atom uas tuaj yeem nyob rau hauv ib qho ntawm ob lub zog hluav taws xob, lub xeev qis (tejzaum nws yog lub xeev hauv av) thiab lub xeev zoo siab, nrog lub zog E1 thiab E2 raws li.
Yog tias lub atom nyob rau hauv lub xeev zoo siab, nws tuaj yeem lwj mus rau hauv lub xeev qis dua los ntawm cov txheej txheem ntawm spontaneous emission, tso tawm lub zog sib txawv ntawm ob lub xeev raws li photon.
Hloov pauv, yog tias lub xeev zoo siab atom raug cuam tshuam los ntawm lub zog hluav taws xob ntawm zaus ν0, nws tuaj yeem tso tawm ib qho photon ntxiv ntawm tib zaus thiab hauv theem, yog li ua rau sab nraud, tawm hauv lub atom hauv qis zog.. Cov txheej txheem no hu ua stimulated emission.
kev sib tw
Qhov tsis tu ncua ntawm proportionality B21 siv nyob rau hauv qhov sib npaug rau kev txiav txim spontaneous thiab induced emission yog hu ua Einstein coefficient B rau qhov kev hloov pauv, thiab ρ(ν) yog hluav taws xob ceev ntawm qhov xwm txheej ntawm zaus ν. Yog li, tus nqi emission yog proportional rau tus naj npawb ntawm atoms nyob rau hauv lub xeev zoo siab N2 thiab qhov ceev ntawm qhov teeb meem photons. Xws li yog lub essencephenomena ntawm stimulated emission.
Tib lub sijhawm, cov txheej txheem ntawm kev nqus atomic yuav tshwm sim, uas tshem tawm lub zog ntawm lub tshav pob, tsa cov electrons los ntawm lub xeev qis mus rau sab saud. Nws qhov nrawm yog txiav txim siab los ntawm qhov sib npaug tseem ceeb.
Yog li, net fais fab tso tawm mus rau hauv ib qho hluav taws xob sib npaug ntawm lub zog ntawm photon h lub sij hawm qhov kev hloov pauv net. Rau qhov no los ua tus lej zoo, qhia txog tag nrho qhov tshwm sim ntawm tus kheej thiab raug tsim tawm, yuav tsum muaj ntau lub atoms hauv lub xeev zoo siab dua li qib qis.
Qhov txawv
Cov khoom ntawm kev txhawb nqa emission piv rau cov khoom siv teeb pom kev zoo (uas nyob ntawm qhov emissions spontaneous emission) yog tias cov emission photons muaj tib zaus, theem, polarization thiab kev taw qhia ntawm kev nthuav tawm raws li qhov xwm txheej photons. Yog li, cov photons koom nrog kev sib koom ua ke. Yog li ntawd, thaum lub sij hawm inversion, optical amplification ntawm qhov teeb meem hluav taws xob tshwm sim.
Kev hloov pauv hluav taws xob
Txawm hais tias lub zog tsim los ntawm kev tawm dag zog yog ib txwm nyob ntawm qhov ntau zaus ntawm thaj teb uas txhawb nqa nws, cov lus piav qhia saum toj no ntawm kev suav nrawm tsuas yog siv rau kev ua kom zoo siab ntawm ib qho kev kho qhov muag, lub zog ntawm stimulated (los yog spontaneous) emission yuav txo qis raws li hu ua kab duab. Txiav txim siab tsuas yog ib qho kev nthuav dav uas cuam tshuam rau atomic lossis molecular resonance, spectral kab duab ua haujlwm tau piav qhia raws li Lorentz faib.
Yog li, qhov kev tawm dag zog tau txo qis los ntawm qhov nocoefficient. Nyob rau hauv kev xyaum, lineshape broadening vim inhomogeneous broadening kuj tuaj yeem tshwm sim, feem ntau yog vim Doppler nyhuv los ntawm kev faib cov velocities nyob rau hauv cov roj ntawm ib tug tej yam kub. Qhov no muaj cov duab Gaussian thiab txo lub ncov lub zog ntawm txoj kab kev ua haujlwm. Hauv qhov teeb meem ua tau zoo, qhov ua tiav lineshape muaj nuj nqi tuaj yeem suav los ntawm kev sib koom ua ke ntawm tus kheej txoj haujlwm ua haujlwm koom nrog.
Kev tawm dag zog tuaj yeem muab lub cev lub cev rau kev nthuav dav kho qhov muag. Yog tias ib qho chaw sab nraud ntawm lub zog txhawb nqa ntau dua 50% ntawm cov atoms hauv av hauv lub xeev kom hloov mus rau lub xeev zoo siab, ces qhov hu ua pej xeem inversion yog tsim.
Thaum lub teeb ntawm qhov tsim nyog zaus dhau los ntawm qhov nruab nrab inverted, photons yog absorbed los ntawm atoms uas nyob twj ywm hauv av los yog txhawb cov atom zoo siab kom emit ntxiv photons ntawm tib zaus, theem thiab kev taw qhia. Txij li thaum muaj ntau atoms nyob rau hauv lub xeev zoo siab tshaj nyob rau hauv lub xeev av, qhov tshwm sim yog ib qho kev nce nyob rau hauv lub input siv.
Radiation absorption
Hauv physics, qhov nqus ntawm hluav taws xob hluav taws xob yog txoj hauv kev uas lub zog ntawm photon absorbed los ntawm teeb meem, feem ntau yog electrons ntawm ib lub atom. Yog li, lub zog hluav taws xob hluav taws xob tau hloov mus rau hauv lub zog sab hauv ntawm lub absorber, xws li cua sov. Qhov txo qis hauv qhov siv ntawm lub teeb yoj propagating nyob rau hauv nruab nrab vim yog nqus ntawm ib co ntawm nws photons feem ntau hu ua attenuation.
Nquag nthwv dej nqustsis nyob ntawm lawv qhov kev siv zog (linear absorption), txawm hais tias nyob rau hauv qee qhov xwm txheej (feem ntau hauv optics) qhov nruab nrab hloov pob tshab nyob ntawm qhov siv ntawm cov nthwv dej sib kis thiab kev nqus txaus.
Muaj ntau txoj hauv kev los txheeb xyuas cov hluav taws xob sai thiab muaj txiaj ntsig zoo npaum li cas hauv ib puag ncig muab, xws li kev nqus coefficient thiab qee qhov cuam tshuam zoo sib xws.
Kev txo qis qis
Ntau yam attenuation yam ntxwv:
- Attenuation factor, uas yog qee zaum, tab sis tsis yog ib txwm, synonymous nrog absorption factor.
- Molar absorption peev yog hu ua molar extinction coefficient. Nws yog qhov absorbance faib los ntawm molarity.
- Qhov loj attenuation factor yog qhov nqus tau faib los ntawm qhov ntom.
- Qhov nqus thiab tawg ntu ntu muaj feem cuam tshuam nrog cov coefficients (absorption thiab attenuation, ntsig txog).
- Extinction hauv astronomy yog sib npaug rau qhov damping factor.
Constant for equations
Lwm yam kev ntsuas ntawm kev nqus hluav taws xob yog qhov nkag mus tob thiab cov nyhuv ntawm daim tawv nqaij, kev nthuav tawm tas li, attenuation tas li, theem tsis tu ncua thiab cov nthwv dej tsis sib haum, tsis yooj yim refractive index thiab extinction coefficient, complex permittivity, hluav taws xob resistivity thiab conductivity.
Absorption
Absorption (tseem hu ua optical ntom) thiab kho qhov muagqhov tob (tseem hu ua optical thickness) yog ob qho kev ntsuas sib cuam tshuam.
Txhua qhov ntsuas no, tsawg kawg rau qee qhov, qhov nruab nrab nqus hluav taws xob ntau npaum li cas. Txawm li cas los xij, cov kws kho mob sib txawv thiab cov txheej txheem feem ntau siv cov txiaj ntsig sib txawv los ntawm cov npe saum toj no.
Qhov nqus ntawm ib yam khoom ntsuas qhov teeb meem ntau npaum li cas yog absorbed los ntawm nws (es tsis txhob xav txog lossis refraction). Qhov no yuav cuam tshuam rau lwm yam khoom ntawm cov khoom los ntawm txoj cai Beer-Lambert.
Kev ntsuas qhov tseeb ntawm qhov nqus ntawm ntau lub wavelengths ua rau nws muaj peev xwm txheeb xyuas cov khoom siv nqus spectroscopy, qhov twg cov qauv yog illuminated los ntawm ib sab. Qee qhov piv txwv ntawm kev nqus yog ultraviolet-pom spectroscopy, infrared spectroscopy, thiab X-ray absorption spectroscopy.
Daim ntawv thov
Kev nkag siab thiab ntsuas qhov nqus ntawm electromagnetic thiab induced hluav taws xob muaj ntau yam kev siv.
Thaum muab faib, piv txwv li, hauv xov tooj cua, nws nthuav tawm ntawm qhov pom.
Qhov kev tawm dag zog ntawm lasers kuj paub zoo.
Nyob rau hauv huab cua thiab huab cua, lub ntiaj teb thiab hauv zos qhov kub thiab txias nyob ntawm ib feem ntawm kev nqus hluav taws xob los ntawm cov pa cua hauv huab cua (piv txwv li, cov nyhuv tsev cog khoom), nrog rau thaj av thiab dej hiav txwv.
Hauv cov tshuaj, X-rays tau nqus mus rau qhov sib txawv los ntawm cov ntaub so ntswg sib txawv (tshwj xeeb, pob txha), uas yog lub hauv paus rau radiography.
Kuj tseem siv hauv chemistry thiab cov ntaub ntawv tshawb fawb, sib txawvcov ntaub ntawv thiab cov molecules yuav nqus hluav taws xob mus rau qhov sib txawv ntawm ntau zaus, tso cai rau cov ntaub ntawv txheeb xyuas.
Nyob rau hauv optics, looj tsom iav dub, xim lim, dyes thiab lwm yam ntaub ntawv zoo sib xws yog tsim tshwj xeeb los coj mus rau hauv tus account seb pom wavelengths lawv nqus thiab nyob rau hauv dab tsi proportions. Cov qauv ntawm tsom iav nyob ntawm cov xwm txheej hauv qab uas txhawb nqa emission tshwm sim.
Nyob rau hauv biology, cov kab mob photosynthetic xav tau lub teeb ntawm qhov tsim nyog wavelength kom absorbed nyob rau hauv lub active cheeb tsam ntawm chloroplasts. Qhov no yog qhov tsim nyog kom lub teeb lub zog tuaj yeem hloov mus rau hauv cov tshuaj muaj zog hauv cov suab thaj thiab lwm cov molecules.
Nws paub hauv physics tias D-thaj tsam ntawm lub ntiaj teb ionosphere tau nqus cov xov tooj cua uas poob rau hauv cov hluav taws xob ntau zaus thiab cuam tshuam nrog hluav taws xob cuam tshuam.
Nyob rau hauv nuclear physics, qhov nqus ntawm cov hluav taws xob nuclear tuaj yeem siv los ntsuas cov qib kua, densitometry, lossis ntsuas tuab.
Cov ntawv thov tseem ceeb ntawm kev cuam tshuam hluav taws xob yog quantum generators, lasers, optical devices.
