Light Source
| A – Lamp Compartment |
| B – Light Source (Hollow Cathode Lamp) |
C – Alignment Knobs |
The
light source generates resonance lines that can be absorbed by atoms of the element of
unknown concentration. The ideal activity
that a light source should produce is a steady, low noise signal with very little
interference and a long operating life. The
common light sources used in atomic absorption spectrophotometry are the hollow cathode
lamps (HCL) and the electrodeless discharge lamps (EDL).
The Perkin-Elmer model 460 uses hallow cathode lamps. The HCL consists basically of three parts: a
sealed glass tube filled with argon or neon, a cathode built from the element of interest,
and an anode. The gas ions are accelerated
ahead the cathode by a high voltage, hitting and displacing atoms of the element that are
then excited by collisions with gas ions. As
atoms suffer excitation they radiate light of the proper wavelength for absorption by
atoms of the same element in the flame. The
HCL can be of two types depending on the material used to build the cathode: single or
multi elements. HCL are commonly use as the
light source for most elements, however with volatile elements short lamp life and low
light intensity may be a problem.