/***

SDFreed

Hwang and Freed, JChemPhys63(1975)4017 http://dx.doi.org/10.1063/1.431841

Meier, Kruk, Gmeiner,Rossler, JChemPhys136(2012)034508

    [f]=Hz

    [n]=spins/m^3

    [d]=m

    [tau]=s

    NP number of points in the integral calculation 

 ***/

double SDFreed(double f, double tau, double n, double d, double NP)

{

    double __JSDFreed_();

    double Kdd1=1.70888e-49;  /* 3/10*(mu0/(4*pi))^2*gamma^4*hbar^2 */

    double RSD;

    RSD=Kdd1*n*tau*pow(d,-3.0)*(__JSDFreed_(f,tau,NP)+4*__JSDFreed_(2*f,tau,NP));

    return RSD;

}