Atomic emissions and absorption Instrumentation I Atomic emissions and absorption 2/12/11

Atomic emission E = hv = h*c/l When excited, an atom will absorb external energy and raise its electrons above the ground state. This is a transient and unstable state. The electrons will return to the ground state, but need to return the energy they absorbed to reach the higher state in discrete quanta of energy.

Every element has a distinct pattern of allowable quanta based on the electron configuration of that element. h = Plank’s constant = 6.626 x 10-34 J*sec The energy is typically given off as light Hydrogen is the easiest to visualize

According to Plank’s equation, each transition can be related to a wavelength

Each element will have a distinctive pattern of emission Hydrogen 434 410 486 656 nm Iron

Note that all wavelength in a spectra do not have the same intensity This can be caused by re-absorbtion or interference) Hg spectrum

Prismatic dispersion

Diffraction. Close point sources

Reflective diffraction

Atomic emission spectroscopy

Getting the best excitation = ICP Induction Coupled Plasma

ICP reduces sample induced interferences- 7000-8000 degree plasma Primarily used in metals analysis Sensitive to 1 part/billion range

Atomic absorption spectroscopy

Example AAS

Comparision

FTIR Absorption of broadband infrared and subsequent analysis of interference

Typical FTIR spectrum

polypropylene Comparison analysis