User:David K. O'Hara/Notebook/physics 307 lab/Electron Spin Resonance Summary

From OpenWetWare
Jump to: navigation, search

Electron Spin Resonance

The purpose of this lab was to find the gs value of the electron. This is done by putting a material sample inside of uniform magnetic field then subjecting the sample to a resonating frequency. The spin flip transition occurs when the the electron can absorb a photon of energy equal to the quantity gsμbB.


Results were somewhat frustrating for this experiment. The setup of the resonating circuit was challenging, and there are some definite redflag moments working with the electrolytic capacitor the circuit uses, but once the circuit was properly setup, the data taking was straightforward.

Disclaimer on data interpretation, covered in my lab notebook [[1]] there is a major error in my data analysis. Using the equations and procedures listed in the lab manual I ended up with a value for gs of about .9, with the accepted value of 2.00232. Looking over the manual I finally decided to use the value B/2 instead of B for the calculations done in the excel spreadsheet included in my lab notebook, with a discussion of possible reasons for the math error.

I ended up with a value for gs of 1.87016 +/-.018513 for the medium coil and 1.87079 +/-.03581 for the large coil.

SJK 18:11, 25 October 2009 (EDT)
18:11, 25 October 2009 (EDT)
Good job reporting uncertainty, but too many digits makes it difficult to read, and would make a reader lack confidence in the result. A better way to report it would be 1.87 +/- 0.02 and 1.87 +/- 0.04. Also, the percent error is interesting, in terms of indicating accuracy...however, much better is to compare this discrepancy with your uncertainty to say whether your measurements are consistent with the accepted value.

The error from the accepted value would be about 6.5%.


This experiment was quite challenging and interesting, and being able to observe electron magnetic resonance was a treat. The systemic error that leads to the whole factor of two issue in this experiment has to be eliminated.SJK 18:39, 25 October 2009 (EDT)
18:39, 25 October 2009 (EDT)
see comments at end of your primary notebook for what I think is the answer to your mystery. Very very good practice on your part to point out the problem, to allow me and other readers to look into the issue further and not be misled.

Some sources of error in the data, would be the way data is read off the oscilloscope, but with the equipment available the data collected was as solid as possible. If I was to run this experiment again I would try to use a different meter for measuring the current just to be sure that the current reading is as precise as possible. The setup of the distance of the helmholtz coils was not precise and since this measurement is what makes all the calculations workout, more time should have been spent on this part of the setup. Any misalignment of the coils would lead to a less uniform B field which could have skewed the resonance data.