FUNCTION VERN16(E,IZZ)
C     ======================
C
C     Photoionization cross-sections for ground states
C       of all Sulfur ions.
C           Verner D.A. et al. 1996, ApJ 465
C           Verner & Yakovlev 1995, A&AS 109, 125
C
      INCLUDE 'IMPLIC.FOR'
      INCLUDE 'BASICS.FOR'
      PARAMETER (T18=1.D-18,MVER=16)
      DIMENSION S0(MVER),E0(MVER),EMX(MVER)
      DIMENSION Y0(MVER),Y1(MVER),YW(MVER),YA(MVER),PV(MVER)
      DIMENSION S95(MVER),E95(MVER),Y95(MVER),YW95(MVER),P95(MVER)
C
      DATA S0/4.564D4,3.136D2,6.666D0,2.606D0,5.072D-4,9.139D0,5.703D-1,
     +        3.161D1,9.646D3,5.364D1,1.275D1,3.49D-1,2.294D4,2.555D1,
     +        2.453D1,2.139D2/
      DATA E0/18.08,8.787,2.027,2.173,0.1713,14.13,0.3757,14.62,0.1526,
     +        10.4,6.485,2.443,14.74,33.1,439.,110.4/
      DATA EMX/170.,184.6,199.5,216.4,235.,255.7,2569.,2641.,2705.,
     +         2782.,2859.,2941.,3029.,3107.,5.D4,5.D4/
      DATA Y0/0.9935,2.782,15.68,19.75,94.24,0.,222.2,18.69,1.615D-3,
     +        17.75,34.26,227.9,2.203D-2,0.,0.,0./
      DATA Y1/0.2486,0.1788,9.421,3.361,0.6265,0.,4.606,0.3037,0.4049,
     +        1.663,0.137,1.172,1.073D-2,0.,0.,0./
      DATA YW/0.6385,0.7354,4.109,1.863,0.788,0.,1.503,1.153D-3,1.492,
     +        2.31,1.678,0.7033,27.38,0.,0.,0./
      DATA YA/1.,3.442,54.54,66.41,198.6,1656.,146.,16.11,1438.,36.41,
     +        65.83,541.1,1.529,38.21,44.05,32.88/
      DATA PV/13.61,12.81,8.611,8.655,13.07,3.626,11.35,8.642,5.977,
     +        7.09,7.692,7.769,25.68,5.037,1.765,2.963/
      DATA S95/1.883D2,1.896D2,1.780D2,2.037D2,2.919D2,4.712D2,1.916D1,
     +         1.931D1,1.946D1,2.041D1,2.101D1,2.087D1,2.233D1,2.293D1,
     +         2.453D1,2.139D2/
      DATA E95/91.52,90.58,92.46,87.44,74.11,57.47,495.2,489.1,493.7,
     +         480.2,475.8,482.8,466.9,466.7,439.,110.4/
      DATA Y95/71.93,75.38,149.8,93.1,48.64,36.1,35.55,50.,35.68,50.,
     +         50.,37.42,50.,44.59,44.05,32.88/
      DATA YW95/0.2485,0.2934,0.02142,9.497D-3,0.02785,0.0248,10*0./
      DATA P95/3.633,3.635,3.319,3.565,4.142,4.742,1.742,1.65,1.737,
     +         1.65,1.65,1.72,1.65,1.668,1.765,2.963/
C
      VERN16=0.
      IVER=IZZ
C
C     1996 Expression
C
      IF(E.LT.EMX(IVER)) THEN
        XX=E/E0(IVER)-Y0(IVER)
        YY=SQRT(XX*XX+Y1(IVER)*Y1(IVER))
        AA=(XX-UN)*(XX-UN)+YW(IVER)*YW(IVER)
        BB=YY**(HALF*PV(IVER)-5.5)
        CC=(UN+SQRT(YY/YA(IVER)))**PV(IVER)
        FY=AA*BB/CC
        VERN16=S0(IVER)*T18*FY
      ELSE
C
C     1995 Expression for high energies
C          (ionization of inner shell electron)
C
        YY=E/E95(IVER)
        XL=0.
        IF(IZZ.LE.6) XL=UN
        Q=HALF*P95(IVER)-5.5-XL
        AA=(YY-UN)*(YY-UN)+YW95(IVER)*YW95(IVER)
        BB=YY**Q
        CC=(UN+SQRT(YY/Y95(IVER)))**P95(IVER)
        FY=AA*BB/CC
        VERN16=S95(IVER)*T18*FY
      END IF
C
      RETURN
      END