1PHYS 6715 - Lecture VI1Lecture VIFluorescence1.Introduction2.Spectroscopy measurements3.Time-domain measurementsPHYS 6715 - Lecture VI2VI-1Introductionenergy1432⎟⎟⎠⎞⎜⎜⎝⎛−⋅=Δ22204118finnhmeEε13.7 eV = 91 nmouter shell: n>1Electronic transitionsPHYS 6715 - Lecture VI3VI-1Introductionenergyω==Δ+→:levelsoscillator1nnEr0rrA5.00±≈−rreV5≈U142.510rad/seck mω→==×Representative values:22J/m106~×→k()2021rrkU−≈m6μλ=6 amu (2 carbon nuclei)m=mid-IRVibrational transitionsPHYS 6715 - Lecture VI4VI-1Introduction212JJEJmr→+Δ=⋅=0.1rnm=eV1023−×≈6 amum=microwave regimeRepresentative values:mm5.010≈→λRotational transitions(J: quantum # of angular momentum)PHYS 6715 - Lecture VI5VI-1IntroductionAbsorption spectrumDNAelectronicvibrationalrotationalPHYS 6715 - Lecture VI6VI-1IntroductionFluorescence•Luminescence is defined as light emission from systems at electronically excited states due to optical excitation with shorter wavelength. •Luminescence can be classified as either fluorescence or phosphorescence.•Fluorescence = luminescence due to electronic transition from singlet excited states. The relaxation times are short, 1~10ns, because large probability of transition to the singlet ground state.•Phosphorescence = luminescence due to electronic transition from triplet excited states. The relaxation times are long, >~1ms, because small probability of transition to the singlet ground state.
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