ADAS Subroutine ccaval

        SUBROUTINE CCAVAL(NUPPER,NLOWER,AVALUE)      
C-----------------------------------------------------------------------
C
C  	*********   FORTRAN77 SUBROUTINE: CCAVAL *********
C
C  	PURPOSE:  EVALUATES HYDROGENIC TRANISITON PROBABILITIES
C		  FOR TRANSITIONS BETWEEN PRINCIPAL QUANTUM SHELLS.
C
C  	CALLING PROGRAM: ADAS312
C
C	INPUT  :
C
C		(I*4)	NUPPER		: UPPER PRINCIPAL QUANTUM
C					  NUMBER.
C		(I*4)	NLOWER		: LOWER PRINCIPAL QUANTUM
C					  NUMBER.
C		
C	OUPUT :
C		(R*8)	AVALUE		: TRANSITION PROBABILITY.
C
C	GENERAL :
C
C		(R*8)	EN		: UPPER PRINCIPAL QUANTUM
C					  NUMBER.
C		(R*8)	EN1		: LOWER PRINCIPAL QUANTUM
C					  NUMBER.
C		(R*8)	X2		: GENERAL VARIABLE
C		(R*8)	X		: GENERAL VARIABLE
C		(R*8)   G		: BOUND-BOUND GAUNT FACTOR.
C
C
C 	ROUTINES:
C
C          ROUTINE         SOURCE       BRIEF DESCRIPTION
C          -------         ------       -----------------
C	    GBB		    ADAS	EVALUATES BOUND-BOUND
C					GAUNT FACTOR.
C	   
C 	CONTACT : HARVEY ANDERSON
C	    	  UNIVERSITY OF STRATHCLYDE
C	          ANDERSON@PHYS.STRATH.AC.UK
C
C 	DATE    : 11/03/99
C
C	VERSION: 1.1						DATE: 17-03-99
C	MODIFIED: HARVEY ANDERSON
C			- FIRST VERSION
C
C-----------------------------------------------------------------------

      INTEGER             NLOWER,      NUPPER
      REAL*8              AVALUE