I started to analyze the EPR spectra of Fe but it is new to me, I dont have enough experience in analyzing epr data. so can I know how i can get the zero field splitting parameters(D,E) from experimental data, I just calculated the g factor? and can I get a software used to simulate the spectra please?
Dear Naglaa Nasralla, I could help you with this. I have some free software which I eventually could send you. But, it would be of great help to you, if yoe showed me the spectra, as I have some experience interpreting EPR spectra. I could quickly let you know whether or not simulations of the spectra would help you. Sincerely, Hogni Weihe ([email protected])
What sort of iron is it? for example heme iron an iron sulfur cluster etc.
If you have an idea whats in your sample you generally look at the literature to see if someone measured the spectrum of something similar and compare it to what you measure.
As for software, if you have matlab you can download for free Stefan Stoll's EasySpin EPR simulation toolkit, which is better than pretty much anything else available at the moment.
If you know the probable structure/ s, then ADF SW can work.
It gives you D,E[ three values of g(g11,g22,g33) along with giso],[three values of hyperfine coupling constant(a11,a22,a33)s along with Aten ] as well as NQR parameters (NQCC, h, verification of Laplace eqution ).
From my own experience, there is SOMETIMES SOME LIMITATIONS for iron (II,III) complexes especially if they are susceptible to show CT and/or SSCO. Then only D, E, NQCC and h parameters can be determined accurately while (g ) and (a) values MAY not be the exact.
Analysis methods depend on which results you wish to obtain. if you wish to qualitatively compare hyperfine splitting or other revealing spectral features evident in Fe complexes with different oxidation states, simply graph and visually compare spectra. I favor using Origin graphing software in Waterfall mode for such comparison . For qualitative analysis (i.e. determining the number of unpaired electrons, you will need to solve integrals wherein you calculate the areas bounded by the x-axis and the region of the spectrum displaying the derivative of the microwave absorption that signifies the electron transition. Some EPR systems let you calculate integrals in situ. Since you will doubtless need to perform many baseline corrections, I recommend downloading the numeric results to Mathlab and calculating the integrals there. Depending on your Mathlab proficiency, you may wish to code a subroutine that uses a scale and slope-manipulating GUI to simplify the procedure. You will also need to construct a calibration curve using a suitable standard (ex: CuSO4, TEMPOL) to yield the average number of unpaired electrons given select dilutions of said standard. The standard should be chosen so as to minimize the curve correlation coefficient, i.e. minimize scatter in the data points used to construct the calibration curve. Compare the integral values you calculate with those comprising your calibration curve to obtain the average number of unpaired electrons in your Fe samples.
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