!------------------------------------------------------------------------------
!
real(fp) FUNCTION SIGCX_Z(EREL,ANEUT)
!
!  3/28/79
!  THIS FUNCTION WAS WRITTEN BY HARRY H. TOWNER OF THE PRINCETON
!  PLASMA PHYSICS LAB.	THIS FUNCTION WILL CALCULATE THE CHARGE
!  EXCHANGE CROSS SECTION AS GIVEN BY EQ. 4 OF RIVIERE'S PAPER.
!
!  PARAMETER LIST:
!  EREL	  - THE RELATIVE ENERGY BETWEEN THE NEUTRAL AND THE CHARGED
!	    PARTICLE.  (KEV)
!	    EG. WNEUT+ANEUT*1.5*TI/APLASMA.
!  ANEUT  - THE ATOMIC WEIGHT OF THE NEUTRAL PARTICLE. (amu)
!
!  Units of SIGCX_Z is m**2
!
!  EE IS THE RELATIVE ENERGY (IN EV) PER AMU.
!============
! idecl:  explicitize implicit REAL declarations:
  use iso_c_binding, only: fp => c_double
  use physconst_mod, only : one,zkev2ev,zcm2tom2
  IMPLICIT NONE
  real(fp) erel,aneut,ee,al10
!============
  EE=EREL*zkev2ev/ANEUT
!  THE CROSS-SECTION IS NOW EVALUATED.
  AL10=log10(EE)
  SIGCX_Z=(1.6666e-16_fp*AL10-2.1505e-15_fp)*AL10+.6937e-14_fp
  SIGCX_Z=SIGCX_Z*zcm2tom2/(one+.1112e-14_fp*EE**3.3_fp)
  RETURN
END FUNCTION SIGCX_Z
!
!------------------------------------------------------------------------------
! 30Jun2000 fgtok -s r8_precision.sub "r8con.csh conversion"
