ADAS Subroutine r8atab

      FUNCTION R8ATAB ( IZ1 , NU , LU , NL , LL )
C
C
C-----------------------------------------------------------------------
C
C  **************** FORTRAN77 REAL*8 FUNCTION: R8ATAB ******************
C
C  PURPOSE: CALCULATES HYDRONIC L RESOLVED A-VALUES.
C
C           ON FIRST CALL WITH VALID INPUT PARAMETERS, FUNCTION SETS UP
C           A TABLE OF A-VALUES. ON SUBSEQUENT CALLS VALUES ARE THEN
C           LOOKED UP.
C
C           FUNCTION CHECKS TO SEE IF A-VALUE IS POSSIBLE AND DIPOLE
C           ALLOWED AND RETURNS ZERO IF NOT.
C
C  CALLING PROGRAM: GENERAL USE
C
C  FUNC:   (R*8)  R8ATAB   = HYDROGEN A-VALUE.
C
C  INPUT:  (I*4)  IZ1      = ION CHARGE.
C  INPUT:  (I*4)  NU       = UPPER VALUE OF N QUANTUM NUMBER.
C  INPUT:  (I*4)  LU       = L QUANTUM NUMBER FOR NU.
C  INPUT:  (I*4)  NL       = LOWER VALUE OF N QUANTUM NUMBER.
C  INPUT:  (I*4)  LL       = L QUANTUM NUMBER FOR NL.
C
C  PARAM:  (I*4)  MXN      = MAXIMUM VALUE OF N QUANTUM NUMBER.
C
C          (I*4)  M        = TABLE INDEX.
C          (I*4)  N1       = N QUANTUM NUMBER LOOP INDEX.
C          (I*4)  L1       = N QUANTUM NUMBER LOOP INDEX.
C          (I*4)  N2       = N QUANTUM NUMBER LOOP INDEX.
C          (I*4)  L2       = N QUANTUM NUMBER LOOP INDEX.
C          (I*4)  J0       = TABLE INDEX.
C
C          (R*8)  Z14      = REAL VALUE = IZ1**4
C
C          (L*4)  LFIRST   = .TRUE.  = FIRST TIME FUNCTION CALLED.
C                            .FLASE. = FUNCTION HAS BEEN CALLED BEFORE.
C
C          (I*4)  MA()     = INDEX TABLE FOR 'ATABLE'.
C                            DIMENSION: REFERENCED BY NU QUANTUM NO.
C          (R*8)  ATABLE() = TABLE OF A-VALUES.
C                            DIMENSION: REFERENCED BY NU, LU, NL, LL
C                                       QUANTUM NUMBERS.
C
C ROUTINES:
C          ROUTINE    SOURCE    BRIEF DESCRIPTION
C          -------------------------------------------------------------
C          I4UNIT     ADAS      RETURNS UNIT NO. FOR OUPUT OF MESSAGES.
C          R8AH       ADAS      RETURNS HYDRONIC A-VALUE.
C
C AUTHOR:   JONATHAN NASH (TESSELLA SUPPORT SERVICES PLC)
C           K1/0/81
C           JET EXT. 5183
C
C DATE:     29/09/93
C
C-----------------------------------------------------------------------
C
C-----------------------------------------------------------------------
      INTEGER             IZ1,         LL,          LU,          NL
      INTEGER             NU