gas_scattering.cc

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/*===========================================================================
  ===  File description
  ===========================================================================*/
 
 
#include "arts_conversions.h"
#include "gas_scattering.h"
#include "matpack_data.h"
#include "check_input.h"
#include <cmath>
 
Vector calc_rayleighPhaMat(const Numeric& theta_rad,
                            const Index& stokes_dim) {
 
  using Math::pow2;
  using Constant::pi;
 
  chk_if_in_range("Scattering angle", theta_rad, 0, pi);
  
  Vector pha_mat_int(6, 0.0);
 
  switch (stokes_dim) {
    case 4:
      pha_mat_int[4] = 0.0;                               //F34
      pha_mat_int[5] = cos(theta_rad);                    //F44 
      [[fallthrough]];
    case 3:
      pha_mat_int[3] = cos(theta_rad);                    //F33 
      [[fallthrough]];
    case 2:
      pha_mat_int[1] = -0.5 * pow2(sin(theta_rad));       //F12 
      pha_mat_int[2] = 0.5 * (1 + pow2(cos(theta_rad)));  //F22 
      [[fallthrough]];
    case 1:
      pha_mat_int[0] = 0.5 * (1 + pow2(cos(theta_rad)));  //F11
  }
  
  pha_mat_int *= 1.5;
  return pha_mat_int;
}