Answer to Question #223451 in Physical Chemistry for DANTEH

Question

Explain in details the theory behind the atomic spectroscopy which embraces AAS, AES and AFS. (ii). Briefly explain the different principles in the AAS, AES and AFS. (iii). Explain how the Hollow Cathode Lamp (HCL) functions and what is its role in the Atomic spectrometry. (iv). Distinguish clearly between Flame photometry and the Electrothermal atomic spectroscopy. 

Answer 1

The technique uses basically the principle that free atoms (gas) generated in an atomizer can absorb radiation at specific frequency.  Atomic-absorption spectroscopy quantifies the absorption of ground state atoms in the gaseous state .

AAS stands for 'Atomic Absorption Spectroscopy' and AES stands 'Atomic Emission Spectroscopy. ' Both of these are spectro-analytical methods used in Chemistry in order to quantify the amount of a chemical species; in other words, to measure the concentration of a specific chemical species.

Principle of operation: In AAS, when monochromatic light is bombarded through the sample the atoms absorb energy, and the extent of absorption is recorded. In AES, the sample which gets atomised in the flame then absorbs the energy through the electrons which get excited.

Hollow Cathode Lamps are ideal source of spectral lines that are used for testing in laboratories. ... Basically Hollow Cathode Effect is electrical conduction at lower voltage. Apart from HCLs, Hollow Cathode Effect gets used in neon signages as well.

A hollow-cathode lamp (HCL) is type of cold cathode lamp used in physics and chemistry as a spectral line source (e.g. for atomic absorption spectrometers) and as a frequency tuner for light sources such as lasers. ... The buffer gas ions will then be accelerated into the cathode, sputtering off atoms from the cathode it.

The main difference between flame photometry and atomic absorption is that in flame photometry the radiation emitted from the flame is measured, and in atomic absorption the decrease in the intensity of the radiation from thehollow cathode due to the absorption by the atoms in the flame is measured.