ADAS Subroutine r8const

      FUNCTION R8CONST( key )
C-----------------------------------------------------------------------
C
C  **************** FORTRAN77 REAL*8 FUNCTION: R8const *****************
C
C  PURPOSE: Returns the fundamental constant corresponding to 'KEY'.
C
C  CALLING PROGRAM: GENERAL USE
C
C  FUNCTION:
C
C  INPUT:  (C*)   KEY   =  Constant selector key
C
C
C ROUTINES:  
C          ROUTINE    SOURCE    BRIEF DESCRIPTION
C          -------------------------------------------------------------
C          I4UNIT     ADAS      RETURNS UNIT NO. FOR OUTPUT OF MESSAGES.
C
C
C NOTES:   i. For Rydberg constant XXRAMS (or XXDAMS) is called to  
C             determine whether the infinite or mass adjusted rydberg 
C             constant is returned.
C            
C         ii. Data is taken from Cohen & Taylor, Rev. Mod. Phys. 59, 
C             p1121 (1987). As recommended in Atomic Data and Nuclear
C             Data Tables.
C
C        iii. Units are CGS.  
C
C
C AUTHOR:  Martin O'Mullane
C
C DATE:    01/04/99
C 
C UPDATE: 
C
C VERSION: 	1.2
C MODIFIED:	MARTIN OMULLANE
C
C-----------------------------------------------------------------------
C
C-----------------------------------------------------------------------
      CHARACTER*(*)       KEY