The role of matrix material and CCl4 (electron acceptor) on the ionization mechanisms of matrix-isolated naphthalene

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Abstract
The effects of matrix atoms (Ne vs Ar), photoionizing energy and CCl4 (electron acceptor) on the ionization mechanisms of naphthalene are discussed through their impact on the strength of the 300–900 nm spectrum of C10H+8. In Ne and Ar matrices containing naphthalene and CCl4, under 10.2 eV VUV irradiation, CCl+4 is predominantly formed (characterized by a broad, strong absorption at 408 nm in a neon matrix), severely limiting the naphthalene cation yield. As shown by Andrews et al. [J. Phys. Chem. 86, 2916 (1982)], with lower energy photon irradiation (5.6 eV), CCl4 is not ionized, but rather acts as a very efficient electron trap in argon, leading to a strong enhancement of the C10H+8 yield. However, naphthalene cations are not produced under the same conditions in a neon matrix. The difference between the ionization mechanism in the two matrices is explained in terms of spin–orbit coupling.