cgsphotoconstants.f90

!>
!! \brief This module contains radiation-related physical constants
!!
!! Module for Capreole / C2-Ray (f90)
!!
!! \b Author: Garrelt Mellema
!!
!! \b Date:
!!
!! \b Version: cgs units
!!

module cgsphotoconstants

  ! A collection of physical constants and conversion factors for 
  ! photo-ionization calculations
  ! Units: cgs
  
  use precision, only: dp
  use cgsconstants

  !	!> Helium ionization potentials (eV)
  !	real(kind=dp), dimension(0:1),parameter :: ethe=(/24.587,54.416/)
  !> Hydrogen cross section
  real(kind=dp), parameter :: sigh=6.30e-18_dp
  !> Helium cross section
  real(kind=dp), parameter :: sighe0=7.83e-18_dp
  !> He+ cross section
  real(kind=dp), parameter :: sighe1=1.58e-18_dp
  !> H ionization energy in frequency
  real(kind=dp), parameter :: frth0=ev2fr*eth0
  !> He ionization energy in frequency
  real(kind=dp), parameter :: frthe0=ev2fr*ethe(0)
  !> He+ ionization energy in frequency
  real(kind=dp), parameter :: frthe1=ev2fr*ethe(1)
  !> Frequency dependence of H cross section parameter
  real(kind=dp),parameter :: betah0=1.0_dp
  !> Frequency dependence of He cross section parameter
  real(kind=dp), dimension(0:1),parameter :: betahe=(/1.0_dp,1.0_dp/)

  !> Frequency dependence of H cross section parameter
  real(kind=dp), parameter :: sh0=2.8_dp
  !> Frequency dependence of He cross section parameter
  real(kind=dp), parameter :: she0=1.7_dp
  !> Frequency dependence of He+ cross section parameter
  real(kind=dp), parameter :: she1=2.8_dp

  !> maximum T_eff for black body
  real(kind=dp), parameter :: thigh=200000.0_dp
  !> minimum T_eff for black body
  real(kind=dp), parameter :: tlow=2000.0_dp
  !real(kind=dp), parameter :: frtop1=700.0*tlow/47979.72484*1e15

  !> Upper limits for integrals: due to arithmetic precision,
  !!     exp(700) exceeds double precision limit
  real(kind=dp), parameter :: frtop1=700.0_dp*tlow*kb/hplanck
  !> Upper limits for integrals: due to the form of the planck
  !!     curve: take 10 times the frequency of maximum intensity
  real(kind=dp), parameter :: frtop2=5.88e-05_dp*thigh*1e15_dp
  
  !> H optical depth fit parameter for frequency range 2
  real(kind=dp) :: tf2h
  !> H optical depth fit parameter for frequency range 3
  real(kind=dp) :: tf3h
  !> He^0 optical depth fit parameter for frequency range 3
  real(kind=dp) :: tf3he0
  ! 
contains

  !> This subroutine initializes the factors needed
  !! to combine the three optical depths (H, He0, He+) 
  !! in the spectral regions where they all occur.
  !! This is from Tenorio-Tagle et al. (1983)
  subroutine ini_factors ( )
    ! 
    tf2h=(0.63*frth0/frthe0)**(she0)
    tf3h=(frth0/frthe1)**(she1)
    tf3he0=(1.51*frthe0/frthe1)**(she1)
  end subroutine ini_factors

end module cgsphotoconstants