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A dynamic relaxation model of the LPV atmosphere is used to examine the behavior of atomic and molecular species in response to the passage of periodic shocks. Gas components include neutral and ionized forms of H, He, and 23 metals, with molecules H2, H2+, and CO. Although the post-shock gas relaxes continually towards an ever-shifting target equilibrium state, many species do not react rapidly enough to reach their equilibrium abundances. Deep in the atmosphere, strong shocks dissociate molecules but high densities permit rapid recombination, resulting in stable, high abundances. Molecules are also stable and abundant in the upper atmosphere, where weak shocks and low densities produce little dissociation. However, at middle layers, only molecules with high dissociation energies (e.g. CO) are stable; those with low energies (e.g. H2) are dissociated by the shock and then are unable to recombine at the reduced densities involved, resulting in a decline in molecular abundance with density throughout this region.
