UV-VIS and Fluorescence Spectroscopy

Question 1

Most common electron transitions?

Answer 1

Pi - Pi*

Question 2

Monochromator UV-VIS Instrument Schematic

Answer 2

Lamp -> Monochromator -> Sample -> Photo Diode -> Data Processor

Question 3

Diode Array UV-VIS Instrument Schematic

Answer 3

Lamp -> Sample -> Diode Array -> Data Processing ->

Question 4

REMEMBER SIMULTAENOUS EQUATIONS

Answer 4

A = ECL
Simultaneous

Question 5

Definition of Fluorescence?

Answer 5

Promotion of an electron from the ground state to a higher electronic state. This occurs due to addition of energetic light.

Question 6

Multiplicity

Answer 6

(n+1) rule

no unpaired spins = singlet (S)
one unpaired spin = doublet (D)
two unpaired spins = triplet (T)
…

Question 7

How are ground and excited states labelled?

Answer 7

Ground is 0
each excited state after that for a particular multiplicity is numbered sequentially starting from 1

Question 8

Fluorescence spectrometer schematic

Answer 8

Lamp -> Excitation monochromator -> Sample Compartment -> Emission Monochromator -> photomultiplier

Question 9

What is stokes shift?

Answer 9

Different between max wavelengths of excitation/absorption peak and the emission peak

Question 10

STOKES SHIFT EQUATIONS

Answer 10

Change in Energy = Energy of excitation/absorption lambdamax - energy of emission lambdamax

Energy at max wavelength = E = (h*c)/Wavelength (IN METRES)