Frequency coalescence

Simulates the coalescence of peaks in an ensemble of variable-frequency oscillators, often encountered with exchanging protons in NMR experiments (also an exercise in using JavaScript generators for signal generation/processing). The ¹H signal emitted by the above system depends on which one of X or Y the H is bonded to. With slow exchange (f_exchange ≪ | f_X-H – f_Y-H |), two distinct peaks result:

Fast exchange (f_exchange ≫ | f_X-H – f_Y-H |) gives a single peak at the average of f_X-H and f_Y-H:

Try it out!

Intall node.js, then

npm install -g typescript
git clone https://github.com/hessammehr/coalescence
cd coalescence
npm install
tsc -w

You will need to fire up a local dev server

# Python 3
python -m http.server
# Python 2
python -m SimpleHTTPServer
# something a bit faster?
caddy -host localhost -port 8000

Then go to http://localhost:8000.

TODO

• Display the (phase-adjusted) real part of the FFT instead of its magnitude.
• Package fft-asm.js as npm package, then pull it in as a proper dependency.

Credits

• g200kg/Fft-asm.js for FFT calculation