I'd like to know the to 5 ways to improve the resolution of an EPR signal to enable the observation of hyperfine splittings. ideally, low cost and practical, easy to do quickly techniques would be very much appreciated. Which techniques would you try first and are likely to make the biggest impact in the spectra. Assume that I am working with organic radical compounds and not inorganic materials.
your question is a little vague. What a kind of ESR spectrometer are you using and what a kind of organic radicals? Is your radical (or future radicals) pure enough and stable?
Do you want to work at room temperature or low temperature?
What a kind of ESR tubes will be used ?
According to your profil, you can perhaps answer if your organic radical chemistry is not top secret!!.
Thank you in advance
See this link too :
https://www.auburn.edu/~duinedu/epr/2_pracaspects.pdf
JRG
Jean, thanks for the link. I'll get back to you with more information about the tubes tomorrow, but can't give you the structure. The radical is a bench stable, neutral organic pi system (CHNO elements). It's pure by elemental analysis and can be recrystallized. The EPR spectra are recorded on an X-band EPR spectrometer (Adani CMS 8400) at room temperature on dilute solutions in CH2Cl2. For the dilute solution spectra, the microwave power was in the region of 0.5−7.0 mW with a modulation frequency of 100 kHz and a modulation amplitude of 1.0 Gpp. We can also run on the solid sample, but cannot do low temperature studies as the instrument is not equipped for this.
Jean,
EPR Tubes are as follows: Sigma-Aldrich Z566535, Wilmad quartz (CFQ) EPR Tubes, O.D. 4 mm L 250 mm
direct link:
https://www.sigmaaldrich.com/catalog/product/aldrich/z566535?lang=en®ion=CY
Dear Jean,
good, If you want to get clear information on hyperfine spliting, record the spectra for your sample in solid and solution state at room temp then at 77 K(liquid nitrogen temp) for solution. Do not increase the micro wave power,
1 mW is enough.
1. low concentration of the sample (avoid Heisenberg broadening)
2. stable radical
3. low microwave power (see Natarajan) - attenuation > 20
4. measure slowly and many points in the area of interest (spectral witdh, time constant) + ideally record one one spectrum (no sampling-overlaying)
5. low modulation (< than expected splittings) 0.1 to 0.001 G are reasonable e.g. for the pyrene radical anion
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