Lecture notes IA
Lecture 1 – spectrometry
Spectroscopy: interaction of different kinds of radiation with matter
- Electromagnetic, acoustic, ion or electron radiation
Spectrometry: intensity of radiation (measured and converted to electronic signal)
Speed = frequency (v) x wavelength speed of light in air = 3.00 x 10^8 m/s
UV-light: 10-400nm
Visible light: 400-800nm
Ray of light in air with higher v has smaller wavelength
Ground state = lowest electronic state
Energy state of chemical species changes when it loses or gains an amount of energy
(photon) which exactly overlaps with the difference in energy between two states
Shorter wavelength = higher energy
- Large transition large energy difference small
wavelength
,Phosphorescence has longer lifetime compared to fluorescence
(fluorescence is usually measured at low concentrations)
< ----------------------- juiste formule! Gebruik P0!
, Part 2 – spectrometry – instrumentation
Single beam spectrophotometer:
Double beam spectrophotometer:
Monochromator: selects specific wavelength
out of beam of mixture of wavelengths
1. Polychromatic light is collimated by 1st mirror
2. Rays fall on reflection grating. Rays of
different wavelengths are diffracted at
different angles
3. Diffracted rays strike the 2nd mirror, which
focuses them at different points of the focal
plane, depending on their wavelength. (only
few wavelengths escape)
Monochromatic: all light beams have the same wavelength
Wider exit slit wider monochromator bandwidth more wavelengths through slit
Electronic transition is much faster than vibration of atoms and rotation of molecules in
solution
Therefore, the molecule needs time after absorption to adjust its geometry
and solvation to the S1 state
Similar events happen for light emission, though fluorescence is slower
Lecture 1 – spectrometry
Spectroscopy: interaction of different kinds of radiation with matter
- Electromagnetic, acoustic, ion or electron radiation
Spectrometry: intensity of radiation (measured and converted to electronic signal)
Speed = frequency (v) x wavelength speed of light in air = 3.00 x 10^8 m/s
UV-light: 10-400nm
Visible light: 400-800nm
Ray of light in air with higher v has smaller wavelength
Ground state = lowest electronic state
Energy state of chemical species changes when it loses or gains an amount of energy
(photon) which exactly overlaps with the difference in energy between two states
Shorter wavelength = higher energy
- Large transition large energy difference small
wavelength
,Phosphorescence has longer lifetime compared to fluorescence
(fluorescence is usually measured at low concentrations)
< ----------------------- juiste formule! Gebruik P0!
, Part 2 – spectrometry – instrumentation
Single beam spectrophotometer:
Double beam spectrophotometer:
Monochromator: selects specific wavelength
out of beam of mixture of wavelengths
1. Polychromatic light is collimated by 1st mirror
2. Rays fall on reflection grating. Rays of
different wavelengths are diffracted at
different angles
3. Diffracted rays strike the 2nd mirror, which
focuses them at different points of the focal
plane, depending on their wavelength. (only
few wavelengths escape)
Monochromatic: all light beams have the same wavelength
Wider exit slit wider monochromator bandwidth more wavelengths through slit
Electronic transition is much faster than vibration of atoms and rotation of molecules in
solution
Therefore, the molecule needs time after absorption to adjust its geometry
and solvation to the S1 state
Similar events happen for light emission, though fluorescence is slower
