Physics307L:People/Cordova/Matt's Excitation Level of Neon Summary

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My lab partner was Sebastian Rosales.
The notebook for this lab can be found here.

Steve Koch 22:23, 21 December 2010 (EST):Good perseverance on this lab. Good discussion of how to improve measurements in the future.


The purpose of this lab is to identify the fact that, at certain energy levels, atoms absorb [math]e^-[/math]s and reach an excited state. Furthermore, we can observe at which point the Neon gas is ionized (ie the [math]e^-[/math] is freed from the atom, creating a positive ion). We will observe this phenomena by measuring the current collected by the metal ring in the bulb of Neon. The idea is that if the [math]e^-[/math] is not at the excitation level, there will be purely elastic collisions and the [math]e^-[/math] will have enough momentum to not be captured by the ring. However, if the [math]e^-[/math] is at the excitation level, there will be inelastic collisions where the speed of the [math]e^-[/math] is reduced enough to be captured by the ring, at which point the current measured in the ring will greatly increase.


  • Multiple current/voltage sources will be in use. Handle with care.
  • Be sure not to exceed 2.5V on [math]V_f[/math]. This could damage the equipment.
  • Don't break the bulb.


  • Soar Corporation DC Power Supply Mod. 7403 ([math]V_f[/math])
  • Kepco Regulated DC Supply Mod. CK60-0.5 ([math]V_A[/math])
  • Tel 2501 Universal Stand
  • Hertz Critical Potential Bulb #2533
  • Tel 2021 Alarmed Meter and Stand
  • Tel 2533.06 Battery Unit
  • Wavetek Voltage Meter

Set Up

Full Setup (without digital Voltmeter)

A detailed set up can be found in Prof. Gold's lab manual. The diagram to the left provides everything necessary to do this lab. And while this diagram seems rather straightforward, Sebastian and I had some trouble with it. The meter which measures the current obtained in the ring was complicated, and always provided a value, whether or not the equipment is set up correct or not. This made it rather difficult to know if we had the correct set up (taking a few data points at different voltages to see if you get coherent data is recommended). Also, while the voltage source has a meter on it, we used a digital voltage meter in order to get a more accurate reading of the voltage.

  • Note: We had some problems keeping all the wires secure. Make sure to double check all wires before taking data.


  • At 2.1V, Neon is observed to have an excitation level at:
    • 18 +/- 0.25 eV
    • 21 +/- 0.25 eV
  • At 1.8V, Neon is observed to have an excitation level at:
    • 16.375 +/- 0.125 eV
    • 18.25 +/- 0.25 eV
    • 18.875 +/- 0.125 eV
    • 20.75 +/- 0.25 eV
  • The ionization level for Neon is 22 +/- 1 eV

The accepted values for the excitation levels of Neon are:

  • 16.7 eV
  • 18.65 eV
  • 19.75 eV
  • 20.1 eV

The accepted value for the ionization level for Neon is

  • 21.56 eV

Our percent error for the measured values are as follows:

  • [math]\frac{16.7-16.375}{16.7}*100=1.9%[/math] error for our first measured excitation level.
  • [math]\frac{18.65-18.25}{18.65}*100=2.1%[/math] error for our second measured excitation level.
  • [math]\frac{19.75-18.875}{19.75}*100=4.4%[/math] error for our third measured excitation level.
  • [math]\frac{20.75-20.1}{20.1}*100=3.2%[/math] error for our final measured level.
  • [math]\frac{22-21.56}{21.56}*100=2.0%[/math] error for our measured ionization level.

A brief discussion on the error can be found in the notebook.