Physics307L:People/Phillips/ESR
Electron Spin Resonance Summary
Data & Results
The notebook entry for this lab can be found here. Along with the excel files ESR1.xls and ESR2.xls.
For this lab, we measured the intrinsic g-factor of an electron. The accepted value for this is:
[math]\displaystyle{ g_{s-acc}=2.0023 }[/math]
We actually obtained two very different values by calcutlating them in slightly different ways:
SJK 23:42, 17 December 2008 (EST)
I looked at your Excel sheet and when I put in the values I get something like 1.95 for the g value. So, I think you guys just made a typo or used the formula incorrectly.
[math]\displaystyle{ g_{s-1}=4.793 \pm .003 }[/math]
[math]\displaystyle{ g_{s-2}=2.086 \pm .002 }[/math]
These values are reported with errors that represent one standard deviation of the mean (found using Excel).
We also calculated the percent error for each of these values:
[math]\displaystyle{ % error_{1}=\frac{|g_{s-acc}-g_{s-1}|}{g_{s-acc}}\times100 }[/math] = 140%
[math]\displaystyle{ % error_{2}=\frac{|g_{s-acc}-g_{s-2}|}{g_{s-acc}}\times100 }[/math] = 4.31%
Some Conclusions
This lab's main issues were just in the setup. This took us about five and a half hours to do correctly, leaving a very short time to collect data. As a result, we would expect our data to lead us to have a rather large difference from the accepted value for gs. This kind of doubt was seen in our first value, where we had a 140% error with respect to the accepted value. Although this seemed quite large, even though we were expecting a large-end error, we decided to report it because it involved methods that we thought to use in our analysis.
The other value, with a much smaller percent error, was done using analysis mirroring that done by last year's student Linh Le, who did this same experiment. We thought this value would also be worth reporting because it seemed to agree so well with the accepted value and was dome in a method that appeared to be legitimate. The large discrepancy in the two reported values could not be very well explained, except that either us or Linh Le messed up by setting axes incorrectly or forgetting a unit conversion.
This lab had little systematic error, but what it did have was bad. First and most important, we could not discern the exact points to make sure that the oscilloscope waves and peaks met at the exact zero point with the peaks oriented symmetrically to the wave troughs. Also, some of our equipment gave us issues from time to time, leading us to doubt some of our instrument readings (the multimeter for measuring current was especially troublesome). Other than this, there was no real systematic error we could think of (except the interference of the earth's magnetic field, which was said to be negligible by the manual).
