I have a joke you have never XENON here before!

Welcome back everyone! As we near the end of the spookiest month of the year, I thought it would be nice to write a blog on an interesting element we can analyze on our instruments: Xenon! This is not an element we use in our daily lives; however, most people have been exposed to it unknowingly.

For starters, have you ever looked up at the night sky and wondered which ‘star’ is constantly flashing as it moves across the sky, then realizing it is just an airplane? Well, those lights are xenon flash lamps, more commonly known as strobe lights, which are used as a method of reducing collisions by increasing visibility.^[1] Another application for xenon is as a biosensor in magnetic resonance imaging (MRI). In short, it has a high polarizability, making it very sensitive to its surroundings.^[2]

Xenon has two isotopes, ¹²⁹Xe and ¹³¹Xe, where the former has a nuclear spin of ½ and a natural abundance of 26%. Take a look at the spectrum below (Figure 1) to see xenon difluoride analyzed in one of our spectrometers!

Figure 1. ¹²⁹Xe NMR (16.7 MHz) spectrum of XeF₂ in CD₃CN.

When we look at the ¹²⁹Xe spectrum, two questions come to mind: why are there three signals and why is the chemical shift so extreme? Firstly, the xenon is bound to two fluorine atoms, each with spin ½, causing the xenon signal to split into a triplet. When we take a look at the coupling constant between ¹²⁹Xe and ¹⁹F (¹J_Xe,F), it comes out to be about 337 Hz, which is why the triplet peaks are spaced so far apart. Secondly, xenon has a wide chemical shift range (approximately 6200 ppm), where its chemical shift is extremely sensitive to solvents, temperature, viscosity, etc. ^[3]

That is it from me, but if you would like to read some other blog posts, I did a cool blog on T1s and as always, if you have any questions or or comments about anything NMR related, do not hesitate to contact us!

References

[1] https://apps.dtic.mil/dtic/tr/fulltext/u2/a045533.pdf (accessed 21-10-2020).
[2] Schröder, L. Phys. Med. 2013, 29, 3-16.
[3] Bardin, V.V.; Frohn, H-J. Magn. Reson. Chem. 2006, 44, 648-650.