Sebastian Excitation Levels of Neon

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21:53, 21 December 2010 (EST):Good job on this lab. I love the honest discussion of the problems / mistakes / ideas for future improvements. Data looks pretty good too.

Contents

Partner

Purpose

The purpose of this lab is to observe and measure the excitation energies of Neon gas. The excitation energy corresponds to the minimum energy required to excite a bound electron of a Neon atom to a higher energy state. Because there are discrete energies at which this occurs, the energies are said to be quantized. We were also trying to find the ionization energy of Neon. The ionization energy is the energy required to remove a bound electron from an atom.

Lab Data

Excitation Levels of Neon Lab Data

Equipment

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

Lab Summary

As stated above, the main goal of this lab was to measure the excitation energies for Neon. This was the easy part of the lab because a good portion of our time was spent trying to get everything connected correctly. The first day, we made our first attempt to set up the lab, but we were unsuccessful at taking data with this setup. Professor Koch came to help us during the last part of the first day. He, much like us, was not very familiar with this lab. So, this was a learning experience for all of us. By looking at the circuit diagram from Professor Gold's Lab manual (this diagram can be found in my primary lab notebook), as well as pictures from a former students lab (I do not recall what student this was because Prof. Koch had the web page up on his personal laptop), we were able to get the picoamplifier working.

On the second day, we had to reconnect everything because it appeared that someone had used some of our cables. With one minor mix up with the ground cable, we were able to get everything up and running in a short time.

We began taking data by doing a rough scan between 0 and 30 Volts. We set the filament voltage to Vf = 2.1V, and took measurements in 1 volt increments. We then plotted the data right then and there to see if we had a graph similar to the one found in Professor Gold's Lab Manual. Our figure was similar, so we decided to do a more refined scan of the portion of the data where there were peaks. We scanned the 15-22 V range incrementing our data points by 0.25 V. We then tried to measure the ionization energy by flipping the battery. We then did the same rough scan from 0-30V in 1V increments. Finally we repeated the first process for collecting the excitation energy with the filament voltage set to Vf = 1.8V. The results of our calculations can be found below.


Note: As explained in the lab manual, it is very important to be still and make sure that nothing is moving near the setup. Any movement can cause for skewed data.

Results

Note: We obtained the values for the excitation energies by finding the minimum peaks on our graphs.
From the Fine Run With Vf = 2.1V, we have the following Excitation Energies:

1st Excitation Energy: not apparent
2nd Excitation Energy: 18.0 eV with a 3.5% error from the accepted value
3rd Excitation Energy: not apparent
4th Excitation Energy: 21.0 eV with a 4.5% error from the accepted value


From the Fine Run With Vf = 1.8V, we have the following Excitation Energies:

1st Excitation Energy: 16.375 eV (we can assume that where there is a horizontal section of the graph, we failed to locate a minimum) with a 1.9% error from the accepted value
2nd Excitation Energy: 18.25 eV with a 2.1% error from the accepted value
3rd Excitation Energy: 18.875 eV (again, the horizontal portion means that we failed to locate the minimum)
4th Excitation Energy: 20.75 eV with a 3.2% error from the accepted value



Ionization Energy - This is where the slope changes from a lower slope, to a higher slope.

For Vf = 2.1V: 22 eV with a 2.0% error from the accepted value
For Vf = 1.8V: 22 eV with a 2.0% error from the accepted value


Because of our increments of 0.25V, all values are assumed to have a +/- 0.25 eV error.

Accepted Values

The accepted values for the excitation levels of Neon are:

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



The accepted Ionization energy for Neon is:

  • 21.56 eV

Conclusions

My partner and I both feel that a much better analysis of the data, and probably much more accurate and precise results, could have been achieved by simply taking more trials. Despite the lack of data, I feel like we learned a lesson on what not to do. We always need to keep in mind what we are trying to get as an end result. At the time, it seemed like we had two trials, and that this would be enough to do at least a decent analysis. Instead, we ended up having two separate sets of data that had to be analyzed separately. Because we treated them separate, we could not do any error analysis other than a simple percent error. We will try to keep this in mind when doing future labs in order to avoid making this mistake again.

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