Studies on photodissociation of dibromoalkane in UV region

摘要

The photodissociation of CH2Br2, 1,2-C2H4Br2 and 1,4-C4H8Br2 near 234 and 267 nm has been studied using resonance-enhanced multiphoton ionization with time-of-flight mass spectrometry. The wavelength dependence of the relative quantum yields Phi(Br), and Phi(Br*) for both Br(P-2(3/2)0) and Br*(P-2(1/2)0) channels was measured. The results indicated that the yields Phi(Br) of C2H4Br2 is larger than that of CH2Br2. And the quantum yields wavelength dependent of C4H8Br2 shows a different tendency compared to CH2Br2 and C2H4Br2. A likely explanation for the different quantum yields relies on the non-adiabatic transitions and avoided curve crossing mechanism. Additionally, ab initio calculations were performed to get potential energy surface curves of CH2Br2 to elucidate the photodissociation channels in UV region. (c) 2005 Elsevier B.V. All rights reserved.