Question

Please compare and contrast the luminescence processes known as fluorescence and phosphorescence using Jablonski diagrams alongside a brief written summary. Please utilize the Jablonski diagram to clearly explain what it means for an emissions spectrum to have “vibrational structure.”

Answer 1

Jablonski Diagram :- S, ZAR So So (Absorption) (Flunoscence) (Phosphorescence) → Thinner layers are Vibronic level and thicker layers are noitadi. electronic level with electronic state. r e V.R z Vibrational relaxation at DD DAA bayo herm S = singlet (electrons are paired) na tri vita o= Ground ? in terms 1,2 = higher J of energy S19 Sq= Singlet first and second excited statē s Solid line ( : light is involved my: Non-nadialive → Jump from one electronic state to another electronic state is possible if only energy matches, ICF)internal conversion (conversion withinsame multipliciti). ii) S₂S , on S1 So (singlet Singlet), van A s üi) Non- radiative ISC = i) Inter system crossing (crossing b/w stalēs of different spin multiplicity) i) $1 +T1 ; but T1 → Sonot) V il) Non-radiative O M IC, ISC happen only when there are stalēs with sam are available. Absorption : Non-radialive Ş Radialive we get/seelight IC: Non-radiative Non-radiative → No light. IRC: Non-radialive II (SnSo) Fluroscence: Radialive (Tm+50) Phosphorescence: Radialive Miminescence : Radialive (n=1 VR: Non-nadialive (4 E is loo small to see visible light) generally), o wyc+ VR: Non-radialīve So,

Time scale of Photonic processes: Absonplion → 10-155 vibrational nelaxalion-10-12 1005 Bonusly a wind Lifetime of excited state (S1)→ 10-10_167s (fluroscence) Inter system crossing 10-10_1085 Internal cosa version - 10-11 10-9 0 tutto Lifelime of excited Statê (T) → 106_1s (Phosphorescence) Falê of a molecule going from so to S2: S i to pii Dway ? Bretve 4 Eli → can there be a transition 8 al -S2 T L from sa to S, in a nadictive . -51 Si → So No. Because IC+VR is much - fluno scence & solda e Tarent faster process than flunoscence. S2 + S0 = flunoscence des i nt o phosphorescence Festablir et goede 4 انا E124 E و ان بسیار بالا ن ا م دیران اشار الى او برای و او را با case 1. Sa So > Fluroscence o ur snil sufral noun bout de case 2. Sa+S4→S0 => [C+VR+flunoscence alionat D umns • If A E between Sq and Sq is small (less than 5000 cm2) then Sy $1 • Sf AE b/w Sq and Sq is larger (>5000 cm?) then S250. LE Cvery few cases). The molecule will stay at lowest vibrational state of first excited singlet stale for nanosecond in case of Sq+51 +50. Otherwise it will go directly from Sa So exhibiting flunoscence. * That process will occur which has higher raté constant. su toe Kasha's nulerinvandt anong metoda to soudruh wianell u In a condensed media the emission occurs from lowest vibrational level of the first excited electronic state. Emission maximum is independent of excitation wavelength. Vavilor nule :- Quantum yield of emission is independent of excitation wavelength. plo , odozd