SUBROUTINE PFIRON(NELEM,ION,TLOG8,POTLOW8,PF)
      REAL*8 TLOG8,POTLOW8,PF
      DIMENSION PFTAB(7,56,10,9)
      DIMENSION POTLO(7),POTLOLOG(7)
      DATA POTLO/500.,1000.,2000.,4000.,8000.,16000.,32000./
      DATA POTLOLOG/2.69897,3.,3.30103,3.60206,3.90309,4.20412,4.50515/
      IF(PFTAB(1,1,1,1).EQ.0.)THEN
      OPEN(UNIT=4,FILE='KU2A:[KURUCZ.SYNTHE]PFIRON.DAT',
     1STATUS='OLD',SHARED,READONLY)
      READ(4,1)PFTAB
    1 FORMAT(26X,7F10.3)
      ENDIF
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C 20.09        56   199526.     4.211     4.211     4.211     4.211     4.211     4.211     4.211
      TLOG=TLOG8
      POTLOW=POTLOW8
      IF(TLOG.GT.4.)GO TO 20
      IF(TLOG.LT.3.7)GO TO 10
      IT=(TLOG-3.7)/.03+21.
      F=(TLOG-(IT-21)*.03-3.7)/.03
      GO TO 30
   10 IT=(TLOG-3.32)/.02+2.
      IT=MAX(IT,2)
      F=(TLOG-(IT-2)*.02-3.32)/.02
      GO TO 30
   20 IT=(TLOG-4.0)/.05+31.
      IT=MIN(IT,56)
      F=(TLOG-(IT-31)*.05-4.)/.05
   30 LOW=1
      IF(POTLOW.LT.POTLO(LOW))GO TO 32
      DO 31 LOW=2,7
      IF(POTLOW.LT.POTLO(LOW))GO TO 35
   31 CONTINUE
      LOW=7
   32 PF=F*PFTAB(LOW,IT,ION,NELEM-19)+
     1   (1.-F)*PFTAB(LOW,IT-1,ION,NELEM-19)
      RETURN
   35 P=(LOG10(POTLOW)-POTLOLOG(LOW-1))/.30103
      PF=P*(F*PFTAB(LOW,IT,ION,NELEM-19)+
     1   (1.-F)*PFTAB(LOW,IT-1,ION,NELEM-19))+
     2   (1.-P)*(F*PFTAB(LOW-1,IT,ION,NELEM-19)+
     3   (1.-F)*PFTAB(LOW-1,IT-1,ION,NELEM-19))
      RETURN
      END