Fluorescence spectroscopy

What is Fluorescence

What is Fluorescence

is when emitted light is at a higher wavelength than excitation light.

Thermal relaxation?

when the excited electron is set to the lowest excitation level S1.

Kasha’s rule?

Photemission happens during transition of the lowest vibrational level (S1) of first excited state, this is Kashas rule.

What is Phosphorescence?

spin turns from singlet (S1) to triplet (T1) which is intersystem crossing then energy returns from lowest excited state (T1) to ground state.

How can you explain Luminescence lifetime

It is the time elapsed between excitation and emission.

What is the idea of a Spectrum

It is the dependence of intensity on wavelength.

Stokes shift?

The excitation and emission spectrums are mirror images of each other and the gap between the difference in their wavelengths is called the stokes shift.

What is a Fluorimeter

It is used to measure fluorescence.

Which Monochromator is the emission side.

The light green Monochromator is the emission side.

cold emission phenomenon?

Light is not generated by high temperatures so molecules can be excited in different ways.

Interpretation of excitation spectrum?

If excitation wavelength is constant as a function of emission wavelength. Represents vibrational levels from the ground

What happens to the emission spectra shape due to change in excitation wavelength

If change is made to the excitation wavelength in the excitation range the emission spectra shape will not change.

Conditions for

Multiplicity (M) is the number of possible orientation states of the magnetic moment assigned to the spin state (S) relative to the directions of the magnetic field, M= 2S+1

Singlet state

This confirms the Pauli exclusion principle by permitting transition, S = 0 and M = 1

Triplet state

This denies Pauli exclusion principle by forbidding transition, S = 1 and M = 3

Reason for the arrangement of Fluorimeter

the arrangement of the second perpendicular to to sample solution is because excitation light reaching the sample can reach the detector and affect results if in linear arrangement but in the perpendicular arrangement we can exclude the light.

Types of luminescence?

Radiative and non radiative(excitation energy to heat energy)

Examples of radiative luminescence

Fluorescence and phosphorescence

What is Luminescence?

Excitation by stimulation and emission energy to the environment in form of EM waves

Quantum yield range?

0 to 1

Quantum yield formula

N(emis)/N(absor) = K(fluor)/K(sum)

N is number of particles and K is probability of transition

Difference between fluorescence and phosphorescence?

Fluorescence is shorter than phosphorescence