      REAL FUNCTION SIGMA(E)
C     Interchange Reactions
C     H^++D_2->HD^++D
C     CROSS SECTION(CM^2)  :SIGMA
C     COLLISION ENERGY(KEV):E
C     JAERI-Data/Code 96-024(1996)
      REAL A(14)
      DATA EMIN,EMAX /2.2E-3,0.1/
      DATA A /2.759E+15,4.000E+00,3.630E-03,3.374E+00,1.081E-03,
     >        -2.703E+00,4.331E-03,1.700E+00,4.284E-1,5*0.0/
      DATA SIGMA0,ER /1.E-16,25.0/
C---+----1----+----2----+----3----+----4----+----5----+----6----+----7--
      F3(X)=SIGMA0*A(1)*(X/ER)**A(2)/(1.+(X/A(3))**(2.*A(2)))
      F4(X)=SIGMA0*A(1)*(X/ER)**A(2)/(1.+(X/A(3))**(A(2)+A(4)))
      F6(X,ALPHA)=SIGMA0*A(1)*(X/ER)**A(2)/
     >            (1.+(X/A(3))**(A(2)+A(4))+(X/A(5))**(A(2)+ALPHA))
      F11(X,ALPHA,BETA)=SIGMA0*A(1)*(X/ER)**ALPHA/
     >            (1.+(X/A(3))**(ALPHA+BETA)+(X/A(5))**(ALPHA+A(6)))
      F12(X,ALPHA,BETA)=F11(X,ALPHA,BETA)
      F13(X,ALPHA,BETA)=SIGMA0*A(1)*(X/ER)**ALPHA/
     >                  (1.+(X/A(3))**(ALPHA+BETA))
C
      SIGMA=0.0
      IF(E.LT.EMIN .OR. E.GT.EMAX) GO TO 9999
      SIGMA=F11(E,A(2),A(4))+A(7)*F11(E/A(8),A(2),A(9))
 9999 RETURN
      END
