UV light and Fluorescent tubes

[Zeynaz]

Homework Statement

In the manufacturing process of computer chips large silicon wafers have to be cleaned. The surfaces that need cleaning are put under a special gas discharge tube. Such a tube emits UV radiation (by ionising mercury atoms inside the tube present as vapour), which produces individual oxygen atoms, which remove any contamination.

An ordinary fluorescent tube is completely coated with a layer of fluorescent powder on the inside. Such a tube contains the same gas mixture as is used for the cleaning of silicon wafers.

Explain on the basis of the operation of the fluorescent powder, whether an ordinary fluorescent tube would be suitable for this cleaning technique.

Relevant Equations

background knowledge

I know that the answer is NO because now there is an extra substance (the fluorescent powder) that is affecting the emission.

However, i don't know how fluorescent powder works in this case. I tried to search it up and only found that Fluorescent powder will 'fluoresce' when it absorbs UV light. But i can't connect the dots in here.

Is it because the UV light that's created by the emission of mercury vapor is absorbed by the powder before it creates oxygen molecules?

 

[Merlin3189]

Yes.
The question says it is the UV light which produces the needed oxygen atoms. If the ordinary tube absorbs all the UV in the flourescent coating inside the tube, then no UV escapes the tube to react with oxygen outside.
(There isn't oxygen inside the tube, but even if there had been, it wouldn't be able to contact the silicon outside the tube.)

The emited light in an ordinary tube is in the visible part of the spectrum, longer wavelength than UV, and does not have the necessary energy to break the O2 bond.