Why an unpaired electron absorbs microwaves
An electron with no partner behaves like a tiny magnet. In a magnetic field its two possible orientations differ in energy. When the energy of the microwaves matches that difference, the sample absorbs. By sweeping the field the spectrometer finds this condition, and the result is a spectrum.
The position of the spectrum gives the g-value, which tells what kind of radical or ion it is. The lines into which the spectrum splits show which nuclei sit close to the electron. A nitroxide radical, for example, gives three equal lines, because the electron feels the nitrogen nucleus.
Session ideas
- Record the spectrum of a stable nitroxide radical in solution, and read the g-value and the splitting. Level: undergraduate
- Dilute the solution and show that the signal grows in proportion to the concentration. Level: undergraduate
- Vary the modulation amplitude and the microwave power, and see how the line shape and height respond. Level: advanced undergraduate and graduate
- Look for stable radicals in everyday materials. Level: undergraduate
- Compare a simple orbital model with the splitting pattern of a small organic radical. Level: graduate
What it adds to a teaching laboratory
- Compact and safe, with no liquid helium and measurements at room temperature
- A spectrum takes minutes, so a group can try several samples in one session
- Students handle the instrument themselves and see the whole path from sample to spectrum
Points that matter in practice
- Only unpaired electrons give a signal, so most ordinary molecules are invisible. This is a strength for the technique and a point to explain to students
- Dissolved oxygen broadens lines, so degassing gives sharper spectra
- Water absorbs microwaves, so aqueous samples need thin capillaries or a special flat cell
- The spectrum is recorded as a first derivative, which has to be explained before students interpret it
- A benchtop instrument records continuous-wave spectra. Pulsed methods are outside its scope
From first demonstration to a teaching routine
MSY Consulting demonstrates the experiments on your own samples, suggests a set of sessions that fits your course, and trains the teaching staff, so that the practicals run on their own.
Let's talk about your application
Send an email describing your instrument and your application, and you will get a reply.
contact@msyconsulting.euMSY CONSULTING SAS · Wissembourg, France · LinkedIn