User:Joseph Frye/Notebook/Physics Junior Lab 307L/NeonExcitation

Excitation Levels of Neon
This lab was done on Mondays 8/13/2010 and 8/20/2010 at the UNM physics department with my lab partner Alex Benedict. We followed experiment 6 outlined in Dr. Gold's lab manual.

Links
My Lab Summary

| Dr. Gold's Lab Manual

Alex Benedict's Lab Notebook

Equipment



 * Hertz Critical Potentials tube filled with neon
 * Tube stand
 * Picoamplifier and Alarmed Meter
 * 2 Power Supplies
 * Digital Multimeter
 * 1.5V AA Battery
 * Cables

Set Up
Figure 6.2 from Dr. Golds Lab Manual

Thanks to Tomas Mondragon for redoing the text on this diagram the resolution of the original image made it almost unreadable. Mondragon's Notebook Fall '08



We first found all of the equipment we needed according to the lab manual and then connected it according to figure 6.2

we measured the current using the pico-amplifier and the accelerating voltage (Va) using the DMM.



Measurements
[[Media:09262010Excitaion of Neon.xls|Download spreadsheet of our data]]

We did a rough scan of the voltages ranging from 0 to 30V in 1V increments on the accelerating voltage with the filament voltage set at 1.8V.

Here is the graph of that data:



After examining the graph we then decided to to another scan from 15V to 22V using 0.1V increments to get better resolution of the area. We did this once with Vf at 1.8V

Here is the graph:



We also did the same range with the same 0.1V increments but used Vf=2.1V



we also flipped the battery and measured Va at 1V intervals from 0V to 25V. but found this data to be less useful.

[[Media:09262010Excitaion of Neon.xls|Download spreadsheet of our data]]

Observations

 * Looking at the data from the measurements we took with Vf=1.8V, there are two major valleys with relative minimums. One at about 18.4V and the other at about 21.3V.  There were also smaller bumps at 16.0V and 16.3V


 * Looking at the data from the measurements we took with Vf=2.1V, there are again two major valleys with relative minimums. One at about 18.0V and the other between 21.0V and 21.1V. There is a strange jump in the current from 15.8V to 15.9V


 * In each case the current grows linearly with voltage after 21.5V

Calculations
According to Ritter from fall of '09, the accepted values for the first two peaks are 16.7eV and 18.65eV. There is also a peak around 20V. From the lab manual, the accepted value for the ionization energy of neon is 21.56 which is consistent with our data because for voltages higher than that our current grew linearly with the voltage as we would expect.

Our results for the first peak are:

(16.3+/-0.1 + 15.8+/-0.1)/2 = 16.1 +/-0.1

error = (16.7-16.1)/16.7 = 3.6% relative error

For the second peak:

(18.4+18.0 +/-0.2)/2 = 18.2 +/-0.1

error = (18.65-18.2)/18.65 = 2.4% relative error

For the ionization energy of neon:

(21.3 + 21.05 +/-.02)/2 = 21.18 +/-0.1

error = (21.56 - 21.18)/21.56 = 1.8% error

Conclusion

 * We found the first peak to be at 16.1eV +/- 0.1eV with relative error compared to the accepted value of 3.6%


 * The second peak at 18.2eV +/- 0.1eV with relative error compared to the accepted value of 2.4%


 * The ionization energy of neon at 21.18eV +/- 0.1eV with relative error compared to the accepted value of 1.8%


 * the +/- 0.1eV uncertainty here comes from our uncertainty in measuring the voltages since we only measured in 0.1V intervals.