What is Exciton Binding Energy? What is Electronic Transitions with extinction coefficients? (Explain concisely)

What is Exciton Binding Energy?
What is Electronic Transitions with extinction coefficients?
(Explain concisely)

Expert Solution

a) Exciton is a Coulomb-correlated electron-hole pair. Frenkel treated the crystal potential as a perturbation to the Coulomb interaction between an electron and a hole which belong to the same crystal cell. This method is most effective in organic molecular crystals. The binding energy of Frenkel exciton (i.e. the energy of its ionisation to a non-correlated electron hole couple) can be of the order of 100-300 meV. Frenkel excitons have been searched for and observed in alkali halides. At present, they are widely studied in organic materials where they dominate the optical absorption and emission spectra. In the end of 1930s the Swiss physicist Gregory Hugh Wannier (1911-1983) and English theorist Sir Nevil Francis Mott have developed a concept of exciton in semiconductor crystals, where the rate of electron and hole hopping between different crystal cells much exceeds the strength of their Coulomb coupling with each other. Unlike Frenkel excitons, Wannier-Mott excitons have a typical size of the order of tens lattices constants and a relatively small bidning energy (typically, a few meV).

b) When interpreting the absorbance and fluorescence spectra of a given molecule, compound, material, or an elemental material, understanding the possible electronic transitions is crucial. Assigning the peaks in the absorption spectrum can become easier when considering which transitions are allowed by symmetry, the Laporte Rules, electron spin, or vibronic coupling. Knowing the degree of allowedness, one can estimate the intensity of the transition, and the extinction coefficient associated with that transition.

Knowing whether a transition will be allowed by symmetry is an essential component to interpreting the spectrum. If the transition is allowed, then it should be visible with a large extinction coefficient. If it is forbidden, then it should only appear as a weak band if it is allowed by vibronic coupling. In addition to this, a transition can also be spin forbidden.

The molar extinction coefficients for d-d transition hover around 100

The molar extinction coefficients for LMCT transitions are around 10^4

genius_generous answered 2 years ago

make an energy level diagram (electronic transitions) of compound Fluorescein

(A) Indicate the selection rules for atomic electronic transitions and the transitions allowed between the electronic...

(A) Indicate the selection rules for atomic electronic transitions and the transitions allowed between the electronic levels 2S1/2, 2P1/2 and 2P3/2 (B) Indicate if the processes of induced emission and spontaneous emission are resonant processes.

What is in the last effects, the nuclear binding energy per atom, and the binding energy...

What is in the last effects, the nuclear binding energy per atom, and the binding energy per nucleon for U-238? (Isotopic mass of U-238=238.05078 amu)

Calculate the total binding energy and the binding energy per nucleon of (a) 7 Be, (b)...

Calculate the total binding energy and the binding energy per nucleon of (a) 7 Be, (b) 56 Fe

Calculate the nuclear binding energy (in joules) and the nuclear binding energy per nucleon of: 113...

Calculate the nuclear binding energy (in joules) and the nuclear binding energy per nucleon of: 113 Cd 48 (112.904401 amu) (Round each final answer to 4 significant figures.) ______J _______J/nucleon

Part1. Calculate the nuclear binding energy (in J) and the nuclear binding energy per nucleon of...

Part1. Calculate the nuclear binding energy (in J) and the nuclear binding energy per nucleon of 241 Pu 94 (241.0568453 amu). Part 2. A freshly isolated sample of 90Y was found to have an activity of 8.2 × 105 disintegrations per minute at 1:00 p.m. on December 3, 2006. At 2:15 p.m. on December 17, 2006, its activity was measured again and found to be 2.2 × 104 disintegrations per minute. Calculate the half-life of 90Y.

Calculate (in MeV) the binding energy per nucleon for 14N. Calculate (in MeV) the binding energy...

Calculate (in MeV) the binding energy per nucleon for 14N. Calculate (in MeV) the binding energy per nucleon for 56Fe. Calculate (in MeV) the binding energy per nucleon for 207Pb.

Indicate whether energy is emitted or absorbed when the following electronic transitions occur in hydrogen: (a) from n = 2 to n = 6,

Indicate whether energy is emitted or absorbed when the following electronic transitions occur in hydrogen:(a) from n = 2 to n = 6,(b) From an orbit of radius 4.76 Å to one of radius 0.529 Å,(c) From the n = 6 to the n = 9 state.

62Ni has the largest known binding energy per nucleon. Calculate the binding energy for the complete...

62Ni has the largest known binding energy per nucleon. Calculate the binding energy for the complete nucleus in kJ/mol and MeV and the binding energy per nucleon in MeV/nucleon given mNi-62 = 61.9283451 amu, mp = 1.00727647 amu, mn = 1.00866492 amu, and 1 amu = 1.6605387310-27 kg. E = ___________________ kJ/mol = ____________________ MeV E/nucleon = ____________________ MeV/nucleon

2Ni has the largest known binding energy per nucleon. Calculate the binding energy for the complete...

2Ni has the largest known binding energy per nucleon. Calculate the binding energy for the complete nucleus in kJ/mol and MeV and the binding energy per nucleon in MeV/nucleon given mNi-62 = 61.9283451 amu, mp = 1.00727647 amu, mn = 1.00866492 amu, and 1 amu = 1.6605387310-27 kg. E = ___________________ kJ/mol = ____________________ MeV E/nucleon = ____________________ MeV/nucleon

Question