add constant to ffhs

src/nmreval/distributions/intermolecular.py

@@ -31,7 +31,7 @@ class FFHS(Distribution):
 
         ret_val = np.array([quad(integrand, 0, np.infty, args=(o, tau0), epsabs=1e-12, epsrel=1e-12)[0] for o in omega])
 
-        return ret_val
+        return ret_val * 54 / np.pi
 
     @staticmethod
     def susceptibility(omega, tau0, *args):