1
$\begingroup$

I am unable to figure out how we get two peaks in the Electron Spin Resonance (ESR) experiment, in which we use Helmholtz coils as B source with modulation, and a basic unit as a source of radio waves.

$\endgroup$
  • $\begingroup$ ESR is electron spin rotation? $\endgroup$ – rob Apr 29 '14 at 19:31
  • $\begingroup$ electron spin resonance $\endgroup$ – kalkanistovinko Apr 29 '14 at 19:42
2
$\begingroup$

You really need to provide more detailed information on your experimental if you hope to get a response. In what follows, I will guess the details of your setup (since you did not provide much), based on a similar setup I once used.

Assuming that the word "modulation" refers to Zeeman modulation created by superimposing a DC and AC voltage on the Helmholtz coil, and that a fixed-frequency radio wave source is used, the amplitude of the Zeeman-modulation-induced fluctuations in radio-wave intensity after passing through the sample is given by $$\Delta I\approx\frac{dI}{dH}\Delta H$$ where $I(H)$ is the absorption intensity as a function of field-strength $H$ and $\Delta H$ is the depth of the Zeeman modulation. Assuming that $\Delta H\ll\sigma$, where $\sigma$ is the width of the peaks, this means that the fluctuation signal measured is actually proportional to $dI/dH$, rather than $I(h)$.

For a Lorentz profile, this gives the following lineshape:

expr = D[1/(x^2 + 1), x];
Plot[expr, {x, -5, 5}]

enter image description here

This is basically the origin of the double-peak shape associated with Zeeman-modulated detection. In essence, you're detecting the derivative of the spectrum, rather than the spectrum itself.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.