ADAS Subroutine etredinv

       FUNCTION ETREDINV( IXTYP , EIJ   , DGEX  , C )
C-----------------------------------------------------------------------
C
C  ******************** FORTRAN 77 FUNCTION: ETREDINV ******************
C
C  PURPOSE:  TO CALCULATE THE ELECTRON ENERGY FROM THE REDUCED ENERGY
C            FOR FOUR TYPES OF TRANSITION 
C
C  CALLING PROGRAM:
C
C  FUNCTION:
C
C  INPUT:    (R*8)    EIJ    =   TRANSITION ENERGY (Eij)
C            (R*8)    DGEX   =   REDUCED ENERGY
C            (R*8)    C      =   ADJUSTABLE SCALING PARAMETER
C            (R*8)    TL     =   Ej/Eij
C            (I)      IXTYPE =   TRANSITION TYPE
C                                1 ELECTRIC DIPOLE
C                                2 NON ELECTRIC DIPOLE
C                                3 SPIN CHANGE
C                                4 OTHER
C
C  OUTPUT:   (R*8)    ETREDINV=   ELECTRON ENERGY
C
C 
C  ROUTINES: NONE
C
C  DATE:     21/06/95			VERSION 1.1
C  AUTHOR:   DAVID.H.BROOKS (UNIV. OF STRATHCLYDE)
C
C-----------------------------------------------------------------------
      INTEGER             IXTYP
      REAL*8              C,           DGEX,        EIJ