ab Assignment: Nuclear Magnetic Resonance

In this lab, you will explore nuclear magnetic resonance with the Teachspin Pulsed/CW NMR Spectrometer and determine the longitudinal and transverse relaxation times in a sample of mineral oil. If time permits you may also determine these parameters in a sample of deionized water.

Part A. Find the Free Induction Decay in mineral oil

Before you begin you will need to familiarize yourself with the equipment by carefully reading the manual provided below. You are encouraged to read the theoretical exposition and sections that describe the experimental apparatus thoroughly before you attempt to make the measurements of the relaxation times. It may also be beneficial to read through and understand qualitatively how an oscilloscope works. The goal in this section is to simply configure the spectrometer to display a frequency induced decay signal on the scope and identify and understand its shape and how adjusting the various inputs affect the signal traced on the scope. The inputs that are relevant are the length of the pulse (A_len), the length of the pulse train (P), and the frequency of the pulse (F) all of these being delivered to the spectrometer by the TeachSpin apparatus. You should also familiarize yourself with tunning the equipment as I will demonstrate to you in class.

Part B. Find the relaxation times T1 and T2 in a sample of mineral oil

The PS_NMR.pdf file linked below has a nice description of how to perform the measurement. In a nutshell, the T1 relaxation time is determined by plotting the height of the FID as a function of the delay time tau between the A and B pulses where the A pulse is set to a length consistent we a 180-degree pulse and the B pulse length set to a 90-degree pulse. The T2 relaxation time is determined using the inverse, A pulse set to 90-degree and B pulse as a 180-degree pulse. The spin-echo signal the results should be plotted verse the delay time tau.

The manual for the spectrometer is available PS2_Manual_1.41.pdf (Links to an external site.): Teachspin PS2-A NMR manual

Laboratory procedure:

1. Inspect the equipment to check if indeed all of the blue coaxial cables are connected properly. Most likely you will not need to adjust any of the cables but be aware that someone may have inadvertently left something connected improperly. Knowing where all the wires go will also help you familiarize yourself with the equipment.
2. Use the NMR probe to check that the spectrometer is properly calibrated. This part is described in the "Getting Started" section. PLEASE DO NOT adjust the capacitors until you have obtained the signal shown on page II-19 of the manual and you have consulted with the instructor. This calibration step will be discussed during the orientation presented by the instructor. Also, it is relatively easy to break the fragile capacitors which will render the equipment useless. Note the voltage readings during the orientation and make sure they are within expectations.
3. Replace the probe with the sample of mineral oil and attempt to find the FID signal on the scope. A nice signal is illustrated on page III-7 of the PS-2 manual. Record the voltage and time sweep on the oscilloscope. Do you understand what these mean? Are they as expected for the sample at hand?
4. During the search for the FID signal play with the spectrometer settings and look through the questions on page III-7. Try to answers them as you progress through the experiment. At first, they may not make sense but by the end of the experiment, most of them should be clear. Do not worry about answering them on your report. But if you would like to comment please feel free to do so.
5. During the experiment, if you feel compelled to include a particular scope display, say the FID, spin-echo or anything else you may do so in one of two ways: take a photo of the scope screen with your phone, or use the USB port to dump the contents of the scope via the out interface. See the scope manuals on the table in the lab.

Some useful links:

• Youtube video on Magnetic Resonance using earth-field NMR experiment. The technology employed is different but the discussion is, particularly the theoretical description is appropriate to the Teachspin device http://www.youtube.com/user/magritek
• PS2_Conceptual_Introduction_to_the_Experiment.pdf (Links to an external site.): Nice summary of the physics and measurement of T1 and T2 with the PS2-A.
• PS2_Manual_1.41.pdf (Links to an external site.): Revised Teachspin PS2-A manual. It supersedes the old manual and a great improvement.
• Pulsed_NMR.pdf (Links to an external site.): Document that features the PS1A experiment, a precursor to the one you will be using, but with an excellent and clear description of the physics, the experimental setup and measurement of two relaxation times T1 and T2. A good supplement to the new manual
• PS2_Aliasing_on_the_Digital_Oscilloscope_Rev_2.0.pdf (Links to an external site.): A note on scope usage that may be a worthwhile read.

Turning in your lab report

Since this lab is on the rather complicated topic of Nuclear Magnetic Resonance a thorough job of describing the physics behind NMR is expected in the introduction along with a detailed explanation of how one extracts the T1 and T2 relaxation times from measurement on the FID and the spin-echo signal. How were the pulse sequences used to extract these values.

Upload your lab report (article) to the Turnitin via the gray box under the "This tool needs to be loaded in a new browser window" line below. It will be graded along the rubric described in this page Grading Rubric. Read through the rubric carefully to maximize your score. If you have any questions please ask. Remember lab reports are usually due on Friday evening after you complete the experiment in class. If you have questions please ask.

Turning in your coding project

There is no coding project with this lab.