private static double CoulombF_Integrate(int L, double eta, double rho)
{
// start at the series limit
double rho0 = 4.0 + 2.0 * Math.Sqrt(L);
if (Math.Abs(rho0 * eta) > 8.0 + 4.0 * L)
{
rho0 = (8.0 + 4.0 * L) / Math.Abs(eta);
}
double F, FP;
CoulombF_Series(L, eta, rho0, out F, out FP);
// TODO: switch so we integrate w/o the C factor, then apply it afterward
if ((F == 0.0) && (FP == 0.0))
{
return(0.0);
}
// integrate out to rho
BulrischStoerStoermerStepper s = new BulrischStoerStoermerStepper();
s.RightHandSide = delegate(double x, double U) {
return((L * (L + 1) / x / x + 2.0 * eta / x - 1.0) * U);
};
s.X = rho0;
s.Y = F;
s.YPrime = FP;
s.DeltaX = 0.25;
s.Accuracy = 2.5E-13;
s.Integrate(rho);
// return the result
return(s.Y);
}
/// <summary>
/// Computes the irregular Coulomb wave function.
/// </summary>
/// <param name="L">The angular momentum number, which must be non-negative.</param>
/// <param name="eta">The charge parameter, which can be postive or negative.</param>
/// <param name="rho">The radial distance parameter, which must be non-negative.</param>
/// <returns>The value of G<sub>L</sub>(η,ρ).</returns>
/// <remarks>
/// <para>For information on the Coulomb wave functions, see the remarks on <see cref="CoulombF" />.</para>
/// </remarks>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="L"/> or <paramref name="rho"/> is negative.</exception>
/// <seealso cref="CoulombF"/>
/// <seealso href="http://en.wikipedia.org/wiki/Coulomb_wave_function" />
/// <seealso href="http://mathworld.wolfram.com/CoulombWaveFunction.html" />
public static double CoulombG(int L, double eta, double rho)
{
if (L < 0) throw new ArgumentOutOfRangeException("L");
if (rho < 0) throw new ArgumentOutOfRangeException("rho");
if ((rho < 4.0) && Math.Abs(rho * eta) < 8.0) {
// for small enough rho, use the power series for L=0, then recurse upward to desired L
double F, FP, G, GP;
Coulomb_Zero_Series(eta, rho, out F, out FP, out G, out GP);
Coulomb_Recurse_Upward(0, L, eta, rho, ref G, ref GP);
return (G);
} else if (rho > 32.0 + (L * L + eta * eta) / 2.0) {
// for large enough rho, use the asymptotic series
double F, G;
Coulomb_Asymptotic(L, eta, rho, out F, out G);
return (G);
} else {
// transition region
if (rho >= CoulombTurningPoint(L, eta)) {
// beyond the turning point, use Steed's method
SolutionPair result = Coulomb_Steed(L, eta, rho);
return (result.SecondSolutionValue);
} else {
// we will start at L=0 (which has a smaller turning point radius) and recurse up to the desired L
// this is okay because G increasees with increasing L
double G, GP;
if (rho < 2.0 * eta) {
// if inside the turning point even for L=0, start at the turning point and integrate in
// this is okay becaue G increases with decraseing rho
// use Steed's method at the turning point
// for large enough eta, we could use the turning point expansion at L=0, but it contributes
// a lot of code for little overall performance increase so we have chosen not to
SolutionPair result;
//if (eta > 12.0) {
// result = Coulomb_Zero_Turning_Expansion(eta);
//} else {
result = Coulomb_Steed(0, eta, 2.0 * eta);
//}
G = result.SecondSolutionValue;
GP = result.SecondSolutionDerivative;
BulrischStoerStoermerStepper s = new BulrischStoerStoermerStepper();
s.RightHandSide = delegate(double x, double U) {
return ((2.0 * eta / x - 1.0) * U);
};
s.X = 2.0 * eta;
s.Y = G;
s.YPrime = GP;
s.DeltaX = 0.25;
s.Accuracy = 2.5E-13;
s.Integrate(rho);
G = s.Y;
GP = s.YPrime;
} else {
// if beyond the turning point for L=0, just use Steeds method
SolutionPair result = Coulomb_Steed(0, eta, rho);
G = result.SecondSolutionValue;
GP = result.SecondSolutionDerivative;
}
// recurse up to desired L
Coulomb_Recurse_Upward(0, L, eta, rho, ref G, ref GP);
return (G);
}
}
}
private static double CoulombF_Integrate(int L, double eta, double rho)
{
// start at the series limit
double rho0 = 4.0 + 2.0 * Math.Sqrt(L);
if (Math.Abs(rho0 * eta) > 8.0 + 4.0 * L) rho0 = (8.0 + 4.0 * L) / Math.Abs(eta);
double F, FP;
CoulombF_Series(L, eta, rho0, out F, out FP);
// TODO: switch so we integrate w/o the C factor, then apply it afterward
if ((F == 0.0) && (FP == 0.0)) return (0.0);
// integrate out to rho
BulrischStoerStoermerStepper s = new BulrischStoerStoermerStepper();
s.RightHandSide = delegate(double x, double U) {
return ((L * (L + 1) / x / x + 2.0 * eta / x - 1.0) * U);
};
s.X = rho0;
s.Y = F;
s.YPrime = FP;
s.DeltaX = 0.25;
s.Accuracy = 2.5E-13;
s.Integrate(rho);
// return the result
return (s.Y);
}
/// <summary>
/// Computes the irregular Coulomb wave function.
/// </summary>
/// <param name="L">The angular momentum number, which must be non-negative.</param>
/// <param name="eta">The charge parameter, which can be postive or negative.</param>
/// <param name="rho">The radial distance parameter, which must be non-negative.</param>
/// <returns>The value of G<sub>L</sub>(η,ρ).</returns>
/// <remarks>
/// <para>For information on the Coulomb wave functions, see the remarks on <see cref="CoulombF" />.</para>
/// </remarks>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="L"/> or <paramref name="rho"/> is negative.</exception>
/// <seealso cref="CoulombF"/>
/// <seealso href="http://en.wikipedia.org/wiki/Coulomb_wave_function" />
/// <seealso href="http://mathworld.wolfram.com/CoulombWaveFunction.html" />
public static double CoulombG(int L, double eta, double rho)
{
if (L < 0)
{
throw new ArgumentOutOfRangeException("L");
}
if (rho < 0)
{
throw new ArgumentOutOfRangeException("rho");
}
if ((rho < 4.0) && Math.Abs(rho * eta) < 8.0)
{
// for small enough rho, use the power series for L=0, then recurse upward to desired L
double F, FP, G, GP;
Coulomb_Zero_Series(eta, rho, out F, out FP, out G, out GP);
Coulomb_Recurse_Upward(0, L, eta, rho, ref G, ref GP);
return(G);
}
else if (rho > 32.0 + (L * L + eta * eta) / 2.0)
{
// for large enough rho, use the asymptotic series
double F, G;
Coulomb_Asymptotic(L, eta, rho, out F, out G);
return(G);
}
else
{
// transition region
if (rho >= CoulombTurningPoint(L, eta))
{
// beyond the turning point, use Steed's method
SolutionPair result = Coulomb_Steed(L, eta, rho);
return(result.SecondSolutionValue);
}
else
{
// we will start at L=0 (which has a smaller turning point radius) and recurse up to the desired L
// this is okay because G increasees with increasing L
double G, GP;
if (rho < 2.0 * eta)
{
// if inside the turning point even for L=0, start at the turning point and integrate in
// this is okay becaue G increases with decraseing rho
// use Steed's method at the turning point
// for large enough eta, we could use the turning point expansion at L=0, but it contributes
// a lot of code for little overall performance increase so we have chosen not to
SolutionPair result;
//if (eta > 12.0) {
// result = Coulomb_Zero_Turning_Expansion(eta);
//} else {
result = Coulomb_Steed(0, eta, 2.0 * eta);
//}
G = result.SecondSolutionValue;
GP = result.SecondSolutionDerivative;
BulrischStoerStoermerStepper s = new BulrischStoerStoermerStepper();
s.RightHandSide = delegate(double x, double U) {
return((2.0 * eta / x - 1.0) * U);
};
s.X = 2.0 * eta;
s.Y = G;
s.YPrime = GP;
s.DeltaX = 0.25;
s.Accuracy = 2.5E-13;
s.Integrate(rho);
G = s.Y;
GP = s.YPrime;
}
else
{
// if beyond the turning point for L=0, just use Steeds method
SolutionPair result = Coulomb_Steed(0, eta, rho);
G = result.SecondSolutionValue;
GP = result.SecondSolutionDerivative;
}
// recurse up to desired L
Coulomb_Recurse_Upward(0, L, eta, rho, ref G, ref GP);
return(G);
}
}
}
