49 lines
1.5 KiB
Fortran
49 lines
1.5 KiB
Fortran
SUBROUTINE IRC(N,T,IC,RNO,SE)
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c =============================
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c
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C IRC CALCULATES THE EXCITATION RATE, SE [cm**3/s], FOR IONIZATION
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C OF HYDROGEN ATOMS FROM STATE N DUE TO ELECTRON COLLISIONS, ASSUMING
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C THE CONTINUUM STARTS AT LEVEL RNO.
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C REF. JOHNSON (1972)
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C
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c a modification of Tim Kallman's XSTAR routine
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c
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INCLUDE 'IMPLIC.FOR'
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IF(IC.NE.1) THEN ! MAB
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CALL SZIRC(N,T,IC,rno,SE)
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RETURN
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END IF
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c
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XO=1.-N*N/RNO/RNO
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YN=XO*157803./(T*N*N)
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IF(N.LE.1) THEN
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AN=1.9603*N*(1.133/3./XO**3-0.4059/4./XO**4+0.07014/5./XO**5)
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BN=2./3.*N*N/XO*(3.+2./XO-0.603/XO/XO)
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RN=0.45
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ELSE IF(N.EQ.2) THEN
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AN=1.9603*N*(1.0785/3./XO**3-0.2319/4./XO**4+0.02947/5./XO**5)
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BN=(4.-18.63/N+36.24/(N*N)-28.09/(N*N*N))/N
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BN=2./3.*N*N/XO*(3.+2./XO+BN/XO/XO)
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RN=0.653
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ELSE
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G0=(0.9935+0.2328/N-0.1296/(N*N))/3./XO**3
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G1=-(0.6282-0.5598/N+0.5299/(N*N))/(N*4.)/XO**4
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G2=(0.3887-1.181/N+1.470/(N*N))/(N*N*5.)/XO**5
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AN=1.9603*N*(G0+G1+G2)
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BN=(4.-18.63/N+36.24/(N*N)-28.09/(N*N*N))/N
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BN=(3.+2./XO+BN/XO/XO)*2.*N*N/3./XO
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RN=1.94*N**(-1.57)
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END IF
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C
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RN=RN*XO
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ZN=RN+YN
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CALL EXPINX(YN,EY)
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CALL EXPINX(ZN,EZ)
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SE=AN*(EY/YN/YN-EXP(-RN)*EZ/ZN/ZN)
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EY=1.+1./YN-EY*(2./YN+1.)
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EZ=EXP(-RN)*(1.+1./ZN-EZ*(2./ZN+1.))
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SE=SE+(BN-AN*LOG(2.*N*N/XO))*(EY-EZ)
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SE=SE*SQRT(T)*YN*YN*N*N*1.095E-10/XO
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RETURN
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END
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