ftirinih
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Nicolet FTIR Beamsplitters
Just how are the KBr beamsplitters configured? Are they simply a slab of KBR with a thin ( quarter wavelength? ) coating of Ge on one face?
I have a few of these and some are fogged, is it possible to refinish (polish) the fogged surfaces?
If so, just what do you use and how do you do it?
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chemrox
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I've got a guy you can talk to about it: Don McCarthy at McCarthy Scientific. If you have any trouble locating them drop me a u2u tomorrow and I
will send you their phone number. He's been very helpful with DIR information and sells DIR and FTIR equipment.
I know that fogged sample cells can be polished and he and I talked about polishing some internal prisms. McCarthy probably has your beam splitter
if the one you have can't be salvaged. What happened? Humidity? Improper storage?
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ftirinih
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I have collected a couple of FTIR modulators from ebay. The mechanical parts are fine, but the KBr has fogged. If the KBr has no anti-reflection
coating (don't see why it would need it since the reflection mismatch is low to start with) it may help to polish it.
I found McCarthy on the web, looks like a good lead. Thanks.
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len1
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| Quote: | Originally posted by ftirinih
I have collected a couple of FTIR modulators from ebay. The mechanical parts are fine, but the KBr has fogged. If the KBr has no anti-reflection
coating (don't see why it would need it since the reflection mismatch is low to start with) it may help to polish it.
I found McCarthy on the web, looks like a good lead. Thanks. |
Hi, I have posted on FTIR beamsplitters elsewhere in this forum. I have also a few instruments from eBay which I managed to get working. The catch
is the beamsplitter. I got an instrument where the owner thought it was fut, but actually he just was not able to adjust it. The point is that
unlress you have a catastrophic failure, the instrument can be got going by sipoly readjusting the mirror alignment to correspond to the slightly
altered profile fo the coating.
And here is the key. Official or second hand outlets are of no use to you if you want to get a spectrometer of eBay going. Thats because a
replacement beamsplitter costs of the order of $3000 US, half price of the instrument is some cases. Hence the prepondarence of cheap FTIR's on eBay.
The beam splitter is indeed a polished KBr crystal (if its a KBr splitter) with a sub-wavelength coating og Ge on one side (and in my case actually in
the middle of two KBr plates) regards Len
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DrP
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I have a KBr disk polishing kit. It was quite expensive for what it is really and it takes a bit a time and practice to get the disks back to looking
crystal clear. They need to be kept desicated for a while also. I guess you could make your own polishing kit out of some very fine wet and dry
paper stretched accross a block and then some polishing felt of some kind for the final polishing. The trick is to keep polishing in all different
directions to obtain an even wear on the disk.
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