Dosimetry

[Amir Rabi'ee]

Hi
i can calculate the number of radicals (that created in alanine) vs dose.
i want to use easyspin for calculating cw-EPR spectrum based on the number of radicals.
can you help me?
Thanks

[Stefan Stoll]

The intensity of an EPR spectrum depends not only the number of radicals, but on a series of instrumental factors such as microwave power and receiver gain. Therefore, EasySpin cannot provide absolute spectral intensities for a given number of radicals.

However, if you have a calibration spectrum, then you will be able to quantify the number of radicals via the double integral or the simulation amplitude. Say you have a spectrum spc0 that you know is due to N0 spins, then if you have second spectrum spc1 from the same species that is a multiple of spc0: spc1 = c*spc0, then you can conclude that the number of radicals in the second sample is c*N0.

[Amir Rabi'ee]

i want to find a relationship between the EPR intensity and the number of radicals when the other conditions(such as microwave power and receiver gain) is constant.
in other word, i want to show that the epr intensity and the number of radicals have a Linear relationship.(i.e. intensity=C*N that C=constant, N=num. of radicals)
there is any way?
Thanks.

[Stefan Stoll]

The EPR signal intensity is proportional to the number of absorbing paramagnetic centers (as long as they are all well separated, in what's called a "magnetically dilute" situation). This is a fact that is established outside of EasySpin, you can't use the software to show or prove it.

But maybe I misunderstand your question. If you want to make a plot of this proportionality, use something like

Code: Select all

clear
Sys.g = 2;
Sys.lwpp = 1;
Exp.mwFreq = 9.5;
[B,spc] = pepper(Sys,Exp);
plot(B,spc,B,2*spc,B,3*spc);
legend('c = c_0','c = 2c_0','c = 3c_0');

[htuner]

The relation between the radiation dose and radiation-induced radicals depend on the radiation yields of the sample which is characterized by G value (defined as the number of radicals produced by radiation energy of 100 eV. (Ikeya M.. , New Applications of Electron Spin Resonance: Dating, Dosimetry, and Microscopy , 1993World Scientific Publishing Co.)). If you want to determine it, you need a reference material which its G value known. Than you can define the correct number of the radical.
From EPR point of view the number of the species that have unpaired electron (radical numbers) is proportional to the area of the absorption curve not to the first derivative signal intensity. You need to double integrate the typical EPR spectrum to find it.
However in EPR dosimetry researchers investigate to find material/materials that present a linear relation to the EPR signal intensity with high radiation yield.

bests

Hasan Tuner

[Amir Rabi'ee]

so, I can't use a software to find a relationship between the EPR intensity and the number of radicals.
Thank Dear Stefan
Thank Dear hasan

[htuner]

You should try to find the double integration of the EPR spectra, this is proportion to the number of the radical. But it is not always lineer. this is the story.

bests
hasan