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*DECK SYBRIJ
SUBROUTINE SYBRIJ(PP,SG,TAU0,TAUI,TAUJ)
*
*-----------------------------------------------------------------------
*
*Purpose:
* Evaluation of the $R_{ij}$ function in 1D slab geometry.
*
*Copyright:
* Copyright (C) 2005 Ecole Polytechnique de Montreal
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version
*
*Author(s): A. Hebert
*
*Parameters: input
* SG specular parity sign.
* TAU0 side to side optical path.
* TAUI optical path in volume i (or volume j).
* TAUJ optical path in volume j (or volume i).
*
*Parameters: output
* PP value of the expression.
*
*-----------------------------------------------------------------------
*
*----
* SUBROUTINE ARGUMENTS
*----
REAL PP,SG,TAU0,TAUI,TAUJ
*----
* SYMMETRIC FORMULA IN (I,J). WE SET POPI <= POPJ
*----
IF(TAUJ.LT.TAUI) THEN
POPI = TAUJ
POPJ = TAUI
ELSE
POPI = TAUI
POPJ = TAUJ
ENDIF
IF((POPI.GT.1.0E-10).AND.(POPJ.GT.1.0E-10)) THEN
PP=0.5*(TABEN(3,TAU0)-TABEN(3,TAU0+SG*POPI)-
1 TABEN(3,TAU0+SG*POPJ)+TABEN(3,TAU0+SG*POPI+SG*POPJ))
ELSE IF(POPJ.GT.1.0E-10) THEN
PP=SG*0.5*POPI*(TABEN(2,TAU0)-TABEN(2,TAU0+SG*POPJ))
ELSE IF(POPI.GT.1.0E-10) THEN
PP=SG*0.5*POPJ*(TABEN(2,TAU0)-TABEN(2,TAU0+SG*POPI))
ELSE
PP=0.5*POPI*POPJ*TABEN(1,TAU0)
ENDIF
RETURN
END
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