Optical path of deuterium lamp and hollow cathode lamp
The deuterium lamp is a continuous radiation source used to correct for non-atomic or background absorption. This light source is a deuterium-filled discharge lamp that emits an intense continuous spectral range from 190 to 400 nm.
This region is the spectral range where atomic absorption is frequently used and background absorption occurs frequently. The diatomic molecule deuterium is used because of its ability to produce a continuous emission spectral band. Deuterium lamps are different in structure and operation from hollow cathode lamps. This lamp integrates a heated electron emission cathode, a metal anode, and a limiting hole between the electrodes.
The deuterium gas is excited using a current of several hundred milliamps during operation. The current passes through the small hole to form a high excitation in a specific area, resulting in a high-intensity emission line. Use a suitable form material so that the emission line passes through and reaches the optical path system of the spectrometer.
In order to achieve excellent background correction results, the light path and energy of the deuterium lamp must be matched with that of the hollow cathode lamp. Deuterium lamp andHollow cathode lampMatching the light path is very important.
If the match is not complete, the atomic density of the two points will be different, resulting in erroneous results. In order to balance the energy of the deuterium lamp and the hollow cathode lamp, the current of the hollow cathode lamp needs to be increased or decreased according to the mutual intensity of the two. Varian's instrument is equipped with an attenuator (automatic in some models) in front of the deuterium lamp, which can reduce its emission intensity to achieve equilibrium with the hollow cathode lamp.
If the energy of the continuous light source is still too strong, it is necessary to reduce the spectral bandwidth. This is because the energy of the continuous light source increases with the increase of the spectral bandwidth, while the energy of the atomic spectral emission line decreases with the increase of the spectral bandwidth.
Similarly, when the energy of the hollow cathode lamp exceeds the deuterium lamp, the spectral bandwidth can be appropriately increased. A balance between the two can be achieved through these methods.
