h*sqrt(82/(4*pi*eps*207*m*R^3*209)) where m=9.1e-31, eps=8.85e-12, h=1.054e-34, R=1.2e-15

Uh oh! Wolfram|Alpha doesn't run without JavaScript.

Please enable JavaScript. If you don't know how, you can find instructionshere.Once you've done that, refresh this page to start using Wolfram|Alpha.