FUNCTION GAUNT(I,FR)
C     ====================
C
C     Hydrogenic bound-free Gaunt factor for the principal quantum
C     number I and frequency FR
C
      INCLUDE 'IMPLIC.FOR'
      PARAMETER (UN=1.)
      DIMENSION CGT(7,10),X(7),FRKW(10)
      DATA CGT/0.,12.803223,-5.5759888,1.2302628,-2.9094219D-3,
     *  7.3993579D-6,-8.7356966D-9,-2.0244141,2.1325684,-1.2709045,
     *  1.1595421,-2.0735860D-3,2.7033384D-6,0.,-0.23387146,
     *  0.52471924,-0.55936432,1.1450949,-1.9366592D-3,2.3572356D-6,
     *  0.,-5.4418565D-2,0.19683564,-0.31190730,1.1306695,
     *  -1.3482273D-3,-4.6949424D-6,2.3548636D-8,-8.9182854D-3,
     *  5.5545091D-2,-0.16051018,1.1190904,-1.0401085D-3,
     *  -6.9943488D-6,2.8496742D-8,-5.5303574D-3,4.1921183D-2,
     *  -0.13075417,1.1168376,-8.9466573D-4,-8.8393133D-6,
     *  3.4696768D-8,-2.2752881D-3,2.3350812D-2,-9.5441161D-2,
     *  1.1128632,-7.4833260D-4,-1.0244504D-5,3.8595771D-8,
     *  -9.7200274D-4,1.3298411D-2,-7.1010560D-2,1.1093137,
     *  -6.2619148D-4,-1.1342068D-5,4.1477731D-8,-4.9576163D-4,
     *  8.5139736D-3,-5.6046560D-2,1.1078717,-5.4837392D-4,
     *  -1.2157943D-5,4.3796716D-8,-2.9467046D-4,6.1516856D-3,
     *  -4.7326370D-2,1.1052734,-4.4341570D-4,-1.3235905D-5,
     *  4.7003140D-8/
      DATA FRKW/6.6D15,9*3.3D15/

      IF(I.LE.10) THEN
          X(5)=FR/2.99793D14
          X(6)=X(5)*X(5)
          X(7)=X(6)*X(5)
          X(4)=UN
          X(3)=UN/X(5)
          X(2)=X(3)*X(3)
          X(1)=X(2)*X(3)
          GAUNT=0.
          DO 10 J=1,7
            GAUNT=GAUNT+CGT(J,I)*X(J)
   10     CONTINUE
      ELSE
        GAUNT=UN
      ENDIF
      RETURN
      END