Mr.Hsiao
CHEM7113 - Atomic Spectroscopy !
!!
Analytical Techniques
"!
Absorption (AAS)
"! Flame AAS "! Vapour
generation AAS furnace (electrothermal) AAS
"! Graphite
"!
Emission (AES)
"! ICP-AES "! AFS
(atomic fluorescence)
Some diagrams and Tables are reproduced from Skoog ‘Principles of Instrumental Analysis’, 5th/6th ed.
1 !
Atomic Spectroscopy !
!!
Electronic transitions : UV - visible radiation excitation of outer-shell electrons of atoms in the gas phase
energy levels of atomic Na
Line thicknesses represent probability of transition!
2 !
Energy Levels of Na vs Mg+ ! energy levels of free Na and Mg+
Na!
Mg+!
Units here are angstroms (0.1 nm)!
3 !
Ca
Ar
Na
Hg
http://astro.u-strasbg.fr/~koppen/discharge/
4 !
Atomic Spectroscopy Options !
Atomic spectra can be measured in 3 ways
"! "! "!
Emission - from thermally excited atoms (and ions) (AES) Absorption - from ground-state atoms (AAS) Fluorescence - photo-excitation of ground-state atoms, followed by emission (AFS)
Fundamentals of AAS, Analytik Jena
5 !
Atomic Spectroscopy !
Atomic transitions suitable for analytical measurements have energies corresponding to UV or visible radiation (vacuum UV can also be used)
!E = h! = hc/" !
Lines used in AAS are usually given in wavelength units "/nm!
6 !
Line Spectra of Atoms !
!!
Atomic linewidths are very narrow ( < 0.01 nm )
Spectrum of a steel hollow cathode lamp
7 !
Band and Continuum Spectra !
Molecular species give band spectra; in the gas phase these can show vibrational structure Continuum emission is observed from hot materials (blackbody radiation); spectral profile depends on the temperature Both must be considered in the context of AAS (and later in ICP-AES), since they can affect the observed signal
8 !
Emission spectrum of brine!
Atomisation methods – overview "
!! !!
Flame:
2000 - 3400 K
Vapour generation: Hydride and cold
!!
Analytical Techniques
"!
Absorption (AAS)
"! Flame AAS "! Vapour
generation AAS furnace (electrothermal) AAS
"! Graphite
"!
Emission (AES)
"! ICP-AES "! AFS
(atomic fluorescence)
Some diagrams and Tables are reproduced from Skoog ‘Principles of Instrumental Analysis’, 5th/6th ed.
1 !
Atomic Spectroscopy !
!!
Electronic transitions : UV - visible radiation excitation of outer-shell electrons of atoms in the gas phase
energy levels of atomic Na
Line thicknesses represent probability of transition!
2 !
Energy Levels of Na vs Mg+ ! energy levels of free Na and Mg+
Na!
Mg+!
Units here are angstroms (0.1 nm)!
3 !
Ca
Ar
Na
Hg
http://astro.u-strasbg.fr/~koppen/discharge/
4 !
Atomic Spectroscopy Options !
Atomic spectra can be measured in 3 ways
"! "! "!
Emission - from thermally excited atoms (and ions) (AES) Absorption - from ground-state atoms (AAS) Fluorescence - photo-excitation of ground-state atoms, followed by emission (AFS)
Fundamentals of AAS, Analytik Jena
5 !
Atomic Spectroscopy !
Atomic transitions suitable for analytical measurements have energies corresponding to UV or visible radiation (vacuum UV can also be used)
!E = h! = hc/" !
Lines used in AAS are usually given in wavelength units "/nm!
6 !
Line Spectra of Atoms !
!!
Atomic linewidths are very narrow ( < 0.01 nm )
Spectrum of a steel hollow cathode lamp
7 !
Band and Continuum Spectra !
Molecular species give band spectra; in the gas phase these can show vibrational structure Continuum emission is observed from hot materials (blackbody radiation); spectral profile depends on the temperature Both must be considered in the context of AAS (and later in ICP-AES), since they can affect the observed signal
8 !
Emission spectrum of brine!
Atomisation methods – overview "
!! !!
Flame:
2000 - 3400 K
Vapour generation: Hydride and cold