Chemical evolution of cold dark clouds in the vicinity of supernova remnants

Abstract

Abstract The supernova explosion increases cosmic ray and x-ray fluxes in the surrounding interstellar medium. Cosmic ray particles and x-ray radiation penetrate nearby molecular clouds and affect the chemical and thermal evolution of the gas. Here we study chemical changes in the dense molecular gas influenced by a sudden increase of the ionization rate that may be caused by the supernova explosion. At the cloud core density 2 × 104 cm−3, the H atom abundance reaches the equilibrium value at about 3 × 104 yr after the change in irradiation conditions. The response time of abundances of icy mantle species is 104 − 105 yr. The abundances of neutral and grain mantle species may not reach their equilibrium values in molecular clouds in the vicinity of’middle-aged’ supernova remnants.