SKIYLD    SKIYLD    SKIYLD    SKIYLD    SKIYLD    SKIYLD    SKIYLD    
          **********************************************
                    **************************
                              ******

SUBROUTINE SKIYLD (IR, ISKWRK, RSKWRK, IYLD, IYION, KYLD, PYLD)
Returns an integer flag to indicate whether reaction IR has yield-
modified species, the species index of its ion, yield-modify flags
for its reactants and products, and parameters for the yield
expression.

INPUT
IR        - Integer scalar, surface reaction index.
ISKWRK(*) - Integer workspace array; dimension at least LENISK.
RSKWRK(*) - Real    workspace array; dimension at least LENRSK.

OUTPUT
IYLD      - Integer scalar, flag for yield-modify reactions;
            1, reaction IR uses yield-modification
            0, no
IYION     - Integer scalar, species index of the ion in a yield-
            modify reaction.
KYLD(*)   - Integer array, yield flags for the species in a yield-
            modify reaction;
            dimension at least MAXSPR, the maximum number of species
            allowed in a surface reaction.
            1, species is yield-modified
            0, no
PYLD(*)   - Real array, parameters for the yield-expression in
            a yield-modify reaction;
            dimension at least NYPAR, the number of parameters
            required.
            If IYLD=1, and KYLD of the Nth species in the reaction
            is 1, the stoichiometric coefficient NU of the species is
            scaled by the results of the expression
               PYLD(1) * [Ei**PYLD(3) - PYLD(2)**PYLD(3)] **PYLD(4)
            where Ei is the ion energy of species IYION.