// and the wavelength (wavl). For a pure material with a given absorption coefficient set concn
// to unity and extCoeff to the value of the absorption coefficient.
// The units of the concentration, the absorption coefficient and the wavelength should match.
public static Complex absToComplex(double riReal, double extCoeff, double concn, double wavl){
Complex ri = new Complex();
ri.reset(riReal, extCoeff*concn*wavl/(4.0D*Math.PI));
return ri;
}
// Returns the absorption coefficient ( units - reciprocal metres) that corresponds
// to the imaginary part of a complex refractive index (riImag) at a wavelength wavl (metres)