      REAL FUNCTION SIGMA(E)
C     Dissociative Collisions
C     H_2+H_2->H^+ (Fast,Total)
C     CROSS SECTION(CM^2)  :SIGMA
C     COLLISION ENERGY(KEV):E
C     JAERI-Data/Code 96-024(1996)
      REAL A(14)
      DATA EMIN1,EMAX1 /2.5E+0,50.0E+0/
      DATA EMIN2,EMAX2 /1.5E+2,6.0E+2/
      DATA A /6.827E-02,5.235E+00,8.514E+01,1.016E+00,8.511E-02,
     >        5.996E+00,1.054E+01,4.292E-01,5.958E-01,4.234E+00,
     >        4*0.0/
      DATA SIGMA0,ER /1.E-16,50.0/
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.GE.EMIN1 .AND. E.LE.EMAX1 .OR. 
     >   E.GE.EMIN2 .AND. E.LE.EMAX2) THEN
        SIGMA=F13(E,A(2),A(4))+A(5)*F13(E/A(6),A(2),A(4))+
     >        A(7)*F13(E/A(8),A(9),A(10))
      END IF
 9999 RETURN
      END
