Vacuum ultraviolet photochemistry: I. Unimolecular decomposition studies of small hydrocarbon clusters by molecular beam photoionization mass spectrometry; II. Photofragment dynamics study of carbon disulfide by high resolution molecular beam laser photofragment time-of-flight mass spectrometry

摘要

The energetic and dissociation dynamics of (C(,2)H(,4))(,2)(\u27+), (C(,2)H(,4))(,3)(\u27+), (C(,3)H(,6))(,2)(\u27+) and (c-C(,3)H(,6))(,2)(\u27+) complexes have been studied by photoionization of neutral van der Waals ethylene dimers and trimers, propylene dimers and cyclopropane dimers. Photoionization efficiency studies of C(,2)H(,4), C(,3)H(,6) and c-C(,3)H(,6) and their clusters yield the ionization energies of (C(,2)H(,4))(,n=1,2,3), (C(,3)H(,6))(,n=1,2) and (c-C(,3)H(,6))(,n=1,2) and the appearance energies of C(,3)H(,5)(\u27+) and C(,4)H(,7)(\u27+) from (C(,2)H(,4))(,2). With the estimated values of (C(,2)H(,4))(,n=2,3,4), (C(,3)H(,6))(,2) and (c-C(,3)H(,6))(,2), the bond dissociation energies of (C(,2)H(,4))(,n=1,2,3)(\u27+) C(,2)H(,4), C(,3)H(,6)(\u27+) C(,3)H(,6) and c-C(,3)H(,6)(\u27+) c-C(,3)H(,6) are deduced. It is concluded that the (C(,2)H(,4))(,3)(\u27+), (C(,3)H(,6))(,2)(\u27+) and (c-C(,3)H(,6))(,2)(\u27+) loose complexes arrange to the common C(,6)H12+ collision complexes prior to fragmentation by comparing the major product channels in the unimolecular decompositions of these species. A new molecular beam laser photofragment time-of-flight mass spectrometer with rotatable beam source and movable detector has been constructed for studying photofragmentation dynamics of polyatomic molecules. The design considerations detailed assembly, and initial tests of this machine are described. The time-of-flight data of carbon disulfide laser photofragmentation at 193 nm have been taken at various beam source angles and fragment flight path lengths. The results give insight into the dynamics of the photofragmentation process;*USDOE Report IS-T-1260. This work was performed under Contract No. W-7405-Eng-82 with the U.S. Department of Energy.