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Registered Member #10
Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424
Steve McConner wrote ...
I'm going to guess copper.
Steve applies the KISS (Keep it simple, stupid!) principle successfully. My electrodes are most likely to be copper of course.
Copper has spectral lines in the green at 5100,5150 and 5220 A respectively. This arc is a capacitative discharge and hence very brief. There is little time for ions from the electrode to transport far along the arc channel. The green dots are copper excitation and the rest of the spectrum is air ionisation of nitrogen, oxygen etc.
So who can tell me what was the other electrode? Not copper. I recognised the metal from the spectrum but didn't understand until I looked more closely at my setupand worked it out. The spectrum is most clearly seen in the oblique view.
Registered Member #10
Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424
The spark hit the galvanised bolt supports. (galvanised = zinc coated) I recognised the zinc "blue triplet" seen on low res spectrscopy. Note that it can't be brass because no copper was present. (Brass = copper 63% and zinc 37%.)
The prize surely is the knowledge gained by all about household metal identification. But I could post you a cookie from Australia....
I might set up a slit with a black background so I can do other wider light sources.
Registered Member #10
Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424
Note that I didn't use a razorblade slit for the spectral pics I showed here. The spark is thin enough so that only the camera rainbow filter is needed. A broader light source would blur out though.
Registered Member #2662
Joined: Fri Jan 29 2010, 10:14AM
Location:
Posts: 36
I do a little spectroscopy on plasmas...
When looking at a low energy corona discharge in dry air (a few cm from the electrode) the spectrum is dominated with Nitrogen emission. More specifically, the Nitrogen second positive series... there's a small emission from N2+ at 391nm and NO below 300nm however you need a better spectrometer to see these. There's little in the visible and IR regions, oxygen normally emits 777nm & 844nm. The emission near the electrodes will look different, especially near the cathode! Arc plasmas have considerable continuum radiation and excited metal lines, as observed in your spectrum... quite interesting really!
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Spark spectroscopy
prize?
