Molecules in Type Ia supernovae

Mechanisms for formation and destruction of molecules in Type Ia supernovae (SNe Ia) are explored and contrasted with those in Type II supernovae (SNe II). In the absence of grains, molecular formation in the highly ionized ejecta is initiated by radiative association and radiative attachment. The molecules are destroyed by charge transfer and by energetic electron impact. The molecular abundances are calculated for the elemental compositions given by SNe Ia models. SNe Ia are an unfavorable environment for molecular formation because of the low gas density and the high-ionization fraction in the ejecta, and the masses of the molecules formed in SNe Ia are many orders of magnitude lower than those in SNe II. It is concluded that molecular formation should have no significant effect on the physical properties of SNe Ia, which is in sharp contrast with the case of SNe II.