Hello!

I need help generating a plot, but I don't understand the mechanics of Mathematica well enough to generate what I need.

I'm trying to plot q as a function of L, and I have the constraints

2 L == z (1+Tanh[z])

and

q == -z^2 / (2 L^2)

I've tried several different approaches, but I can't get what I need.

The closest I've come is to use ContourPlot[], as described at https://mathematica.stackexchange.com/questions/22445/plotting-the-solutions-to-a-transcendental-equation. With this technique, I am able to plot z as a function of L:

ContourPlot[ 
 L == z  (1 + Tanh[z])/2), {z, 0, 5}, {L, 0, 
  10}]  (* Not the plot I need *)

Unfortunately, I don't see how to extend it to plotting q as a function of L.

Any help would be most appreciated.

Thanks,

Chris

P.S. This is the non-dimensionalized energy, q, of the double Dirac well problem as a function of the non-dimensionalized separation, L.