Spectroscopy and photodissociation of size-selected (CH3I)n+ cluster ions

✍ Scribed by Jack A. Syage; Jhobe Steadman

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 987 KB
• Volume: 159
• Category: Article
• ISSN: 0168-1176
• DOI: 10.1016/s0168-1176(96)04446-1

✦ Synopsis

The resonant photodissociation of (CH,l)z cluster ions (n = 1-5) was studied in a crossed molecular-electron-laser beam apparatus. These results were complemented by a study of the ionization/dissociation as a function of variable energy electron ionization (EI). The fragmentation that first appears as the EI energy is raised is loss of CHj. This channel is particularly strong for n = 3. The lower energy dissociation of neutral 1, on the other hand, is essentially quenched for cluster sizes of n > 2. Intermolecular dissociation (evaporation) of CH31 was evident, but was not extensive, based on a minor sensitivity of the cluster ion distribution to El energy. The photodissociation of (CH31)i resulted in different dissociation behavior than for EL Resonant excitation of monomer CH,I' to the predissociative A electronic state gave only I + CH;. A state excitation of the cluster ions, on the other hand, resulted only in intermolecular dissociation. The photoexcitation cross-sections for the A 'E1,2 +X 2E1,2 transition are presented as a function of cluster size n. A two-photon dissociation channel is also identified and the crosssections and dissociation products are reported. Finally, the frequency resolved photofragment excitation spectra of CH31' and (CH31)i are compared.