# Electron Spin Resonance (ESR) Experiment: the two peaks

+ 1 like - 0 dislike
5951 views

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.

This post imported from StackExchange Physics at 2014-05-04 11:25 (UCT), posted by SE-user kalkanistovinko
retagged May 4, 2014
ESR is electron spin rotation?

This post imported from StackExchange Physics at 2014-05-04 11:25 (UCT), posted by SE-user rob
electron spin resonance

This post imported from StackExchange Physics at 2014-05-04 11:25 (UCT), posted by SE-user kalkanistovinko

+ 2 like - 0 dislike

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}]


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.

This post imported from StackExchange Physics at 2014-05-04 11:25 (UCT), posted by SE-user DumpsterDoofus
answered Apr 29, 2014 by (50 points)

 Please use answers only to (at least partly) answer questions. To comment, discuss, or ask for clarification, leave a comment instead. To mask links under text, please type your text, highlight it, and click the "link" button. You can then enter your link URL. Please consult the FAQ for as to how to format your post. This is the answer box; if you want to write a comment instead, please use the 'add comment' button. Live preview (may slow down editor)   Preview Your name to display (optional): Email me at this address if my answer is selected or commented on: Privacy: Your email address will only be used for sending these notifications. Anti-spam verification: If you are a human please identify the position of the character covered by the symbol $\varnothing$ in the following word:p$\hbar$ysicsOverflo$\varnothing$Then drag the red bullet below over the corresponding character of our banner. When you drop it there, the bullet changes to green (on slow internet connections after a few seconds). To avoid this verification in future, please log in or register.