User:Chad A McCoy/Notebook/Jr. Lab/2008/12/06

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Electron Spin Lab: 11/24-12/1/2008 SJK Incomplete Feedback Notice Incomplete Feedback Notice My feedback is incomplete on this page for two reasons. First, the value of the feedback to the students is low, given that the course is over. Second, I'm running out of time to finish grading! SJK 17:38, 18 December 2008 (EST) 17:38, 18 December 2008 (EST) See Boleszek's page too, but I think most of my comments there are specific to his analysis. The lab for this week was measuring the g-factor for the intrinsic spin of an electron. Raw data and notes on procedure can be found here As the apparatus included Helmholtz coils, we had to calculate the magnetic field between the coils using the formula: [math]\displaystyle{ \mathrm{B}=\frac{\mu\,{R}^{2}N I}{({R}^{2}+{x}^{2})^{3/2}} }[/math] For our coils, [math]\displaystyle{ R=.0675 m }[/math], [math]\displaystyle{ x=R/2 }[/math], and [math]\displaystyle{ \mu=4 \pi * 10^{-7} }[/math] Plugging those values in, we came out with the result that [math]\displaystyle{ \mathrm{B}=0.004263{I} }[/math] As the objective of this lab was to find the g-factor for the spin of the electron, we could relate the energy difference between the spin-up and spin-down states with the energy of the resonance photon. That relationship is given by: [math]\displaystyle{ {h}{\nu}={g_{s}}{\mu_{B}}{B} }[/math], where h is Planck's constant, g is the spin factor, mu_B is the Bohr magneton, and B is the magnetic field strength. Therefore [math]\displaystyle{ g_{s}=\frac{h}{.004263 \mu_{B}} \frac{\nu}{I}=1.677*10^{-8}\frac{\nu}{I} }[/math] Doing the calculations I came out with a value of g being .8498, with error being .0072. Calculating off a linear fit, the generated value of g was .796 with error .013. Using the calculated value as my final answer, gives me the final value as: [math]\displaystyle{ g_{s}=.8498(72) }[/math] If I compare this value to the accepted value of g, being 2.0023, I find that my answer differs from the accepted value by over 100 times the standard error, meaning that it is very likely that there was a major systematic error that resulted in my answer being that extreme.SJK 17:39, 18 December 2008 (EST) 17:39, 18 December 2008 (EST) Boleszek and other groups also getting off by more than factor of 2...so I suppose it's not very likely to be a calculation error, and must be a systematic error as you say...not sure what though. The excel file that contains all my calculations can be found at Media:Electron Spin Resonance.xls