Looking for an economical calibration light source at ~ 400nm

[flecom]

hecd will get you 325nm no?

[Xytrell]

^I think you missed the economical part

These spectrometers don't go that low anyway. 350 is pretty much the limit.

[flecom]

ive seen some go pretty cheap on ebay... but ya not cheaper than $20

[rhd]

IF not the AR1 lamp, why do I just not carefully pack up a penray and loan it to you.
Steve

not sure if this is an ar1 or 2 but you can have it if you want it.Attachment 30093Attachment 30094

Hey guys,

For some reason the thread subscriptions stopped coming to me via email, and I assumed there had been no further activity on this thread.

Thank you both for the very kind offers. In either case, I wouldn't feel right borrowing or accepting for free, something of this nature. Borrowing a bulb of any sort sounds like a recipe for disaster with two-way shipping involved (and I'm in Canada). Similarly, I'd want to pay you for that AR bulb.

So if one or either of these offers is still on the table, I would love to purchase either item. When I initially said that I was looking for an "economical" source, I didn't mean to imply that I needed something for free I was really just thinking that I needed to avoid a really expensive "lab grade" calibration source. But I'm quite happy to spend some money to get something accurate and useful.

That said, I'm going to go try a few fluorescent bulbs and see what I can identify. If that ends up being sufficient, I'll update the thread.

EDIT: That was a great suggestion. The G-Line was weak, but it was exactly what I needed. I re-calibrated my meter using the G-Line, plus 473, 532 and 589nm DPSS. It might make sense for me to do something similar with a mid 600s range known wavelength also. Do you think something as simple as this:
http://www.ebay.com/itm/B7A-Miniatur...ht_1904wt_1139
Would allow me to calibrate using the (relatively lower powered) lines at 627 and 630 ?
http://physics.nist.gov/PhysRefData/...neontable2.htm

It might be challenging in that some of Neon's other lines would be fairly powerful. In the end, I'd be calibrating with:
- CFL G-Line at: 435.8
- Neon at: 461
- DPSS at: 473
- DPSS at: 532
- DPSS at: 589
- Neon at: 627 or 630

Even though that the calibration requires a 3rd order polynomial, I think I can use as many calibration points as I want in computing it.

[Xytrell]

This is what shows up for me in neon's red spectrum (glow-lamp indicator):

[rhd]

Xytrell: Thank you

There's a line that's showing up at 626.64950, which is what I'm going to use - I can see that line clearly in your output.

[mixedgas]

Be careful on the flourescent lamp cal, some of the new lamps use a neon-krypton mix and almost no mercury.

Steve

[rhd]

Be careful on the flourescent lamp cal, some of the new lamps use a neon-krypton mix and almost no mercury.

Steve

Interesting. Well, there WAS a line in this particular bulb around 435.8. I assumed this was the G-line from mercury. If indeed this was a neon krypton mix, then there's nothing strong (it seems) in neon around that range. What there IS, is a krypton line at 435.5. That's pretty close - close enough that I'm not feeling bad about the calibration.

Any way to verify what a CFL would be filled with?

[mixedgas]

.

Any way to verify what a CFL would be filled with?[/QUOTE]

A USB spectrometer?

Seriously, there should be a transparent part of the bulb in the base some where. Cathodes in the mixed fill lamps will have a orange glow of neon recombination lines around one of the electrodes.

Mercury will usually emit its green and UV lines when the cathode is heated before the lamp arc starts. The Krypton will NOT glow with just a hot cathode. 12V of voltage drop across the hot cathode is enough to ionize the mercury but not the krypton. This was used to make UV lights for aircraft cockpits in World War II, just take a 24V bulb and add pure mercury to the lamp before sealing.

Steve

[Xytrell]

Even in the low-mercury lamps, mercury is still the primary way to excite the phosphors, isn't it?

[rhd]

Even in the low-mercury lamps, mercury is still the primary way to excite the phosphors, isn't it?

For the CFL, I'd located a fairly old bulb that I'm certain has a Mercury fill. Even if it didn't, it would still be a Krypton line at 0.3nm from the Mercury G Line, so the impact on calibration would be negligible. I think I found a final calibration setup, and I'd happily receive any critique of it that anyone might want to contribute:

435.8 - Mercury G Line (from a CFL)
473.? - DPSS
532.? - DPSS
589.? - DPSS
632.8 - HeNe

I need to locate the precise DPSS wavelengths, but I'll do that before undertaking my final calibration. I think I have them written somewhere. From memory, 473 isn't exactly 473.0.