50 lines
2.0 KiB
Fortran
50 lines
2.0 KiB
Fortran
FUNCTION TOPBAS(FREQ,FREQ0,TYPLV)
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C ==================================
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C
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C Procedure calculates the photo-ionisation cross section SIGMA in
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C [cm^2] at frequency FREQ. FREQ0 is the threshold frequency from
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C level I of ion KI. Threshold cross-sections will be of the order
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C of the numerical value of 10^-18.
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C Opacity-Project (OP) interpolation fit formula
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C
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INCLUDE 'PARAMS.FOR'
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PARAMETER (E10=2.3025851)
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PARAMETER (MMAXOP = 200,! maximum number of levels in OP data
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+ MOP = 15 )! maximum number of fit points per level
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CHARACTER*10 IDLVOP(MMAXOP) ! level identifyer Opacity-Project data
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CHARACTER*10 TYPLV
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COMMON /TOPB/ SOP(MOP,MMAXOP) ,! sigma = alog10(sigma/10^-18) of fit point
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+ XOP(MOP,MMAXOP) ,! x = alog10(nu/nu0) of fit point
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+ NOP(MMAXOP) ,! number of fit points for current level
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+ NTOTOP ,! total number of levels in OP data
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+ IDLVOP ,! level identifyer Opacity-Project data
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+ LOPREA ! .T. OP data read in; .F. OP data not yer read in
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DIMENSION XFIT(MOP) ,! local array containing x for OP data
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+ SFIT(MOP) ! local array containing sigma for OP data
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C
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C Read OP data if not yet done
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C
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TOPBAS=0.
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IF (.NOT.LOPREA) CALL OPDATA
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X = LOG10(FREQ/FREQ0)
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DO IOP = 1,NTOTOP
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IF (IDLVOP(IOP).EQ.TYPLV) THEN
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C level has been detected in OP-data file
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IF (NOP(IOP).LE.0) GO TO 20
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DO IFIT = 1,NOP(IOP)
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XFIT(IFIT) = XOP(IFIT,IOP)
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SFIT(IFIT) = SOP(IFIT,IOP)
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END DO
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SIGM = YLINTP (X,XFIT,SFIT,NOP(IOP),MOP)
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SIGM = 1.D-18*EXP(E10*SIGM)
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TOPBAS=SIGM
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GO TO 10
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END IF
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END DO
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10 RETURN
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C Level is not found ,or no data for this level, in RBF.DAT
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20 WRITE (61,100) TYPLV
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100 FORMAT ('SIGMA.......: OP DATA NOT AVAILABLE FOR LEVEL ',A10)
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RETURN
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END
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